To automate the shift operation of a synchronous meshing type transmission by the positional control of a shift select actuator.

This control device of the synchronous meshing type automatic transmission comprises a shift select actuator 5 for switching a plurality of gear stages of a synchronous meshing type staged transmission, a shift position sensor 61 for detecting the shift position of an automatic transmission, a select position sensor 62 for detecting the select position of the automatic transmission, an engine rotation speed sensor 15 for detecting the rotating speed of an engine 1, and a control unit 4 for controlling the shift select actuator (5) based on the outputs from these sensors. If the shift position and select position are not in neutral positions when a key switch is turned on, the shift select actuator 5 is controlled to return to the neutral position.