To provide a mode transition control device for a hybrid vehicle that can achieve smooth mode transition and acceleration at the time of the mode transition under the condition of the zero revolution of a motor-generator and when a driver's acceleration demand is large.

In the hybrid vehicle provided with a driving force synthesizing transmission TM that has differential gears on which four or more input and output elements are arranged on a collinear figure, that allocates an input from an engine E to one of two elements arranged inside the input and output elements, and an output shaft OUT to a driving system to the other, and that connects a first motor-generator MG1 and a second motor-generator MG2 to each of two elements arranged at both outsides of the inside elements, an acceleration-responsive mode-transition control means is provided that controls torque in such a way that no assist torque is added on the motor-generator at the side making the revolutions zero, at the time of the mode transition from "a first traveling mode", in which the zero-revolution of the motor-generator is made a condition for the mode transition, to "a second traveling mode" and when the driver's acceleration demand is a set point or larger.

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