A fuel temperature estimation device that can improve the estimation accuracy of a fuel temperature in each part of a fuel channel, is provided. In the invention, the fuel temperature estimation device estimates the fuel temperature of each part of the fuel channel in a vehicle (for example, an injection nozzle, a pressure accumulator, a high-pressure pump), and includes a flow rate measuring device (SR6) that measures a fuel flow rate of a fuel return system (Lf11 to Lf17) of the fuel channel and a controller (50). The controller (50) includes a fuel temperature correction unit (53) that corrects an estimated fuel temperature in a fuel injection system (3) based on the fuel flow rate of the fuel return system (Lf11 to Lf17), and has a function of estimating the fuel temperature using the fuel flow rate of the fuel return system (Lf11 to Lf17) as a parameter.