A temperature correcting device includes: a power supply that supplies electric power to a terminal machine; a lapsed time obtain part that acquires a lapsed time after the power supply stops the supply of electric power; a temperature detector disposed in the terminal machine to detect a temperature inside the terminal machine as an internal temperature; and an external temperature estimation part that estimates a temperature out of the terminal machine as an external temperature by correcting the internal temperature using a temperature correction value which changes with the lapsed time.