A gear shift control device for controlling a hybrid vehicle drive system (1) including an engine (2), an automated transmission (3), a clutch (4), and a motor generator (5), includes a torque indication means for indicating a driver request torque (Tdrv) determined in accordance with an operation amount of an accelerator operated by a driver, a power generation interruption means changing a vehicle state to an engine driven state using all of the engine torque (Te) when a preliminary gear shift condition is satisfied in a state where the engine (2) drives a driving wheel (91) and the motor generator (5) is actuated to generate an electric power, a gear shift control means reducing the engine torque (Te) and generating an assist torque (Tast) by actuating the motor generator (5), disconnecting the clutch (4), and returning the clutch (4) to a connected state after changing gear sets of the gear train when a gear shift condition of the automated transmission (3) is satisfied.