To provide a heat exchanger and a vehicular air conditioner capable of reducing the size and weight of a device.

This heat exchanger is characterized by having a first heat exchange means 32 for exchanging heat between cooling water and air for cooling a vehicular driving device, and a second heat exchange means 36 for exchanging heat between the cooling water of exchanging heat by this first heat exchange means 32 and a high temperature-high pressure refrigerant delivered from a compressor.