To prevent a gear come-off phenomenon while avoiding an operation delay of a transmission.

An electric air type mechanical transmission 100 comprises: a mechanical transmission body 10; air cylinders 16, 17 for shift/select-operating the transmission body; a lever position detection means 23 for detecting a position of a shift lever 22; a gear position detection means 26 for detecting a gear position of the mechanical transmission body 10; a controller 21 for starting the select/shift operation when the lever position detection means detects a gear-in operation, and finishes the shift operation after the lapse of a prescribed time 1 after the gear position detection means detects gear-in; and a vehicle speed detection means 27 for detecting a vehicle speed. The controller 21 extends the prescribed time T1 when the vehicle speed detection means 27 detects a vehicle stop state, and continues the shift operation until the extended prescribed time elapses or the vehicle speed detection means detects a traveling state.