diff --git a/README.md b/README.md
index 3213370..9da2b3e 100644
--- a/README.md
+++ b/README.md
@@ -174,6 +174,15 @@ There are some configs you need to change in the files below
 | HMD_LDAP_PROVIDERNAME | `My institution` | Optional name to be displayed at login form indicating the LDAP provider |
 | HMD_SAML_IDPSSOURL | `https://idp.example.com/sso` | authentication endpoint of IdP |
 | HMD_SAML_IDPCERT | `/path/to/cert.pem` | certificate file path of IdP in PEM format |
+| HMD_SAML_ISSUER | no example | identity of the service provider (optional, default: serverurl)" |
+| HMD_SAML_IDENTIFIERFORMAT | no example | name identifier format (optional, default: `urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress`) |
+| HMD_SAML_GROUPATTRIBUTE | `memberOf` | attribute name for group list (optional) |
+| HMD_SAML_REQUIREDGROUPS | `Hackmd-users` | group names that allowed (use vertical bar to separate) (optional) |
+| HMD_SAML_EXTERNALGROUPS | `Temporary-staff` | group names that not allowed (use vertical bar to separate) (optional) |
+| HMD_SAML_ATTRIBUTE_ID | `sAMAccountName` | attribute map for `id` (optional, default: NameID of SAML response) |
+| HMD_SAML_ATTRIBUTE_USERNAME | `mailNickname` | attribute map for `username` (optional, default: NameID of SAML response) |
+| HMD_SAML_ATTRIBUTE_DISPLAYNAME | `displayName` | attribute map for `displayname` (optional, default: NameID of SAML response) |
+| HMD_SAML_ATTRIBUTE_EMAIL | `mail` | attribute map for `email` (optional, default: NameID of SAML response if `HMD_SAML_IDENTIFIERFORMAT` is default) |
 | HMD_IMGUR_CLIENTID | no example | Imgur API client id |
 | HMD_EMAIL | `true` or `false` | set to allow email signin |
 | HMD_ALLOW_PDF_EXPORT | `true` or `false` | Enable or disable PDF exports |
@@ -251,6 +260,7 @@ There are some configs you need to change in the files below
 | mattermost | `/auth/mattermost/callback` |
 | dropbox | `/auth/dropbox/callback` |
 | google | `/auth/google/callback` |
+| saml | `/auth/saml/callback` |
 
 # Developer Notes
 
diff --git a/lib/config/environment.js b/lib/config/environment.js
index e339832..3b2e34a 100644
--- a/lib/config/environment.js
+++ b/lib/config/environment.js
@@ -75,7 +75,18 @@ module.exports = {
   },
   saml: {
     idpSsoUrl: process.env.HMD_SAML_IDPSSOURL,
-    idpCert: process.env.HMD_SAML_IDPCERT
+    idpCert: process.env.HMD_SAML_IDPCERT,
+    issuer: process.env.HMD_SAML_ISSUER,
+    identifierFormat: process.env.HMD_SAML_IDENTIFIERFORMAT,
+    groupAttribute: process.env.HMD_SAML_GROUPATTRIBUTE,
+    externalGroups: process.env.HMD_SAML_EXTERNALGROUPS ? process.env.HMD_SAML_EXTERNALGROUPS.split('|') : [],
+    requiredGroups: process.env.HMD_SAML_REQUIREDGROUPS ? process.env.HMD_SAML_REQUIREDGROUPS.split('|') : [],
+    attribute: {
+      id: process.env.HMD_SAML_ATTRIBUTE_ID,
+      username: process.env.HMD_SAML_ATTRIBUTE_USERNAME,
+      displayName: process.env.HMD_SAML_ATTRIBUTE_DISPLAYNAME,
+      email: process.env.HMD_SAML_ATTRIBUTE_EMAIL
+    }
   },
   email: toBooleanConfig(process.env.HMD_EMAIL),
   allowemailregister: toBooleanConfig(process.env.HMD_ALLOW_EMAIL_REGISTER),