An image forming system comprises an access control part, a storage part, an extraction part, and an acquisition part. The access control part determines whether to allow or prohibit access to a security image in which a password for access control is embedded. The storage part stores sharing member information which is information on sharing members who are users allowed to share the security image and a check image which is an image for check on the security image, being associated with each other. The extraction part for extracts the check image out of one or more images including the check image on the basis of a determination result on coidentity between the security image and each of the one or more images. The acquisition part acquires the sharing member information associated with the check image. Further, the access control part allows a login user who logs in to the image forming system to have access to the security image without requiring the login user to enter the password on condition that the login user is determined to be one of the sharing members on the basis of the sharing member information.