To provide a utilization device capable of efficiently utilizing waste heat from a heat treatment device.

In the heat utilization device which utilizes the heat of the in-furnace heat of continuous annealing equipment composed a heating zone, a soaking zone and a cooling zone, or a heating zone, an overaging zone, a cooling zone, an overaging zone and a cooling zone, the heat utilization device is characterized by comprising a Stirling engine which absorbs the heat in the heating zone, the soaking zone, or the overaging zone, and generates power at a gable wall on an inlet/outlet side one of the heating zone, the soaking zone and the overaging zone.