To obtain a transmission of a simple structure wherein a temperature fluctuation range of a working fluid can be reduced.

In the transmission 10, a heat-storage-material heat exchanger 26 acting as a heat storage body is provided in an oil pan 16 constituting a circulation path where an ATF acting as a working fluid circulates. The heat-storage-material heat exchanger 26 includes a latent heat storage material which makes phase transition from a solid phase to a liquid phase by heat exchange between the high-temperature ATF and itself to absorb melting heat from the ATF and contrarily makes the phase transition from a liquid phase to a solid phase by heat exchange between the low-temperature ATF and itself to dissipate the heat of solidification.

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