To increase the quantity of generated heat of a CaO/Ca(OH)2 chemical heat pump and improve the efficiency of heat exchange.

For this heat exchanger, disc-like trays 10 capable of being halved at least at the face passing through the center are arranged in many stages, and a pipe 6 for heat exchange is passed through the recess made at the center of the trays 10, and heaters 5 are arranged in plural recesses made at the periphery of the trays, and the tray is charged with a medium for heat exchange. This can be provided with radial fins 11 inside the tray 10.