The invention discloses an automatic assembly machine for assembling an encoder for an intercom. The automatic assembly machine includes a case, a controller, a rotation disc, a cam divider assembly, an upper manual placement mechanism, a stopping base mounting mechanism, a first film sheet mounting mechanism, a second film sheet mounting mechanism, a first rubber rotation sheet mounting mechanism, a first body mounting mechanism, a second rubber rotation sheet mounting mechanism, a second body mounting mechanism, an oil coating mechanism, a riveting mechanism, a discharging mechanism and detection assemblies; a plurality of working station clamps are movably arranged on a circumferential edge of the rotation disc; In assembly, the upper manual placement mechanism transfers a manual placement shaft core sleeve to a matched working station clamp, and then the stopping base, the first film sheet, the second film sheet, the first rubber rotation sheet, the first body, the second rubber rotation sheet, the second body are mounted successively, the oil coating mechanism performs oil coating after the second body is mounted, the riveting mechanism rivets all the parts through rivets to form a finished product, and the discharging assembly sends the finished product to a collection box. The automatic assembly machine is easy to use, is high in assembly efficiency, is high in yield, is simple to maintain, and is long in service life.