The present invention provides a transmission control device for a vehicle capable of changing a threshold of a shift map for determining shift-up, thereby preventing occurrence of the shift-up during depression of an accelerator and preventing occurrence of a torque interruption. In a transmission control device for a vehicle 1 including a T/M-ECU 50 which automatically performs shift control for switching a plurality of shift gears of a transmission 20 for shift-up or shift-down, the T/M-ECU 50 has a shift threshold setting unit 54 which sets a shift threshold to be used for the shift control, on the basis of an operation plan or a surrounding state of the vehicle 1, and the shift threshold setting unit 54 sets the shift threshold to perform the shift control on the transmission 20 so as not to perform the shift-up of the transmission 20 during acceleration of the vehicle 1.