Vehicular air-conditioning device capable of inhibiting liquid return and generation of noise in an accumulator on startup of a compressor, and improving reliability and comfort. A controller lets a refrigerant discharged from a compressor 2 radiate heat in a radiator 4, and decompresses the refrigerant from which the heat has been radiated, to let the refrigerant absorb heat in an outdoor heat exchanger 7, thereby heating a vehicle interior. On startup of the compressor 2, the controller continues an operation at a predetermined startup number of revolution for a predetermined time, and then raises a number of revolution of the compressor 2 to a predetermined target number of revolution at a predetermined rising speed, and changes the startup number of revolution of the compressor 2 so as to lower the startup number of revolution as the outdoor air temperature is higher, on the basis of an outdoor air temperature.