Provided is a warming device which can efficiently warm a blood product and inhibit a liquid in a warming flow path from exceeding an upper limit temperature thereof when liquid delivery of the blood product is stopped. The warming device includes the warming flow path in which the blood product flows and a heat plate which is in contact with the warming flow path to supply heat to the warming flow path. On the heat plate, a heater in a predetermined pattern corresponding to the warming flow path is disposed. The heater is disposed such that an amount of heat generation toward the warming flow path decreases in stages from an upstream side toward a downstream side in the warming flow path and that a decrease rate of the amount of heat generation at each of the stages decreases from the upstream side toward the downstream side.