To provide an engine start control device used in combination with an active vibration isolation support device so as to suppress the transmission of engine vibration, caused by initial explosion generated at the time of engine starting, to a vehicle body.

An ACM_ECU71 transmits gain of the vibration caused by initial explosion to an Engine-AT_ECU73 as an electric current control command value when engine rotation speed Ne reaches a threshold value Neth in a motoring state. The Engine-AT_ECU73 acquires required input vibration value from the electric current control command value, and controls initial explosion by adjusting initial explosion energy to conform to the required input vibration value in an engine start control section 211a.