A vehicular cooling device comprising: a heat medium circuit in which a heat medium circulates; an engine configured to generate a waste heat in accordance with operation of the engine and supply the waste heat to the heat medium; a heat exchanger configured to exchange heat between the heat medium and a lubricant lubricating a transmission of a vehicle; and a heater configured to heat the lubricant that is inside the heat exchanger, wherein the heat exchanger includes a heat exchange portion configured to exchange heat between the lubricant and the heat medium, the heat exchange portion is located inside the heat exchanger, characterized in that the heat exchanger further includes a first surface through which the lubricant flows in and out of the heat exchanger, wherein the first surface is an upper surface of the heat exchanger having a circular shape and being provided with a lubricant inlet port and a lubricant outlet port, a second surface through which the heat medium flows in and out of the heat exchanger, wherein the second surface is a lateral surface of the heat exchanger having a curved shaped and being provided with a heat medium inlet port and a heat medium outlet port, a third surface that is a surface different from the first surface and the second surface, wherein the third surface is a bottom surface of the heat exchanger having a circular shape and being not provided with any port, and wherein the heat exchange portion is located closer to the third surface than to the first surface and the second surface, and the heater is provided on the third surface. a heat medium circuit in which a heat medium circulates; an engine configured to generate a waste heat in accordance with operation of the engine and supply the waste heat to the heat medium; a heat exchanger configured to exchange heat between the heat medium and a lubricant lubricating a transmission of a vehicle; and a heater configured to heat the lubricant that is inside the heat exchanger, wherein the heat exchanger includes a heat exchange portion configured to exchange heat between the lubricant and the heat medium, the heat exchange portion is located inside the heat exchanger, characterized in that the heat exchanger further includes a first surface through which the lubricant flows in and out of the heat exchanger, wherein the first surface is an upper surface of the heat exchanger having a circular shape and being provided with a lubricant inlet port and a lubricant outlet port, a second surface through which the heat medium flows in and out of the heat exchanger, wherein the second surface is a lateral surface of the heat exchanger having a curved shaped and being provided with a heat medium inlet port and a heat medium outlet port, a third surface that is a surface different from the first surface and the second surface, wherein the third surface is a bottom surface of the heat exchanger having a circular shape and being not provided with any port, and a first surface through which the lubricant flows in and out of the heat exchanger, wherein the first surface is an upper surface of the heat exchanger having a circular shape and being provided with a lubricant inlet port and a lubricant outlet port, a second surface through which the heat medium flows in and out of the heat exchanger, wherein the second surface is a lateral surface of the heat exchanger having a curved shaped and being provided with a heat medium inlet port and a heat medium outlet port, a third surface that is a surface different from the first surface and the second surface, wherein the third surface is a bottom surface of the heat exchanger having a circular shape and being not provided with any port, and wherein the heat exchange portion is located closer to the third surface than to the first surface and the second surface, and the heater is provided on the third surface.