A chemical heat storage device heats a subject to be heated existing in a pipe. The chemical heat storage device includes a reactor that generates heat by chemically reacting with a reaction medium, an absorber that causes an absorbent to absorb and stores the reaction medium, and a connection tube that is connected to the reactor and absorber, for the reaction medium to migrate through. The reactor includes a solid reaction material disposed along an outer peripheral surface of a place where the subject exists in the pipe and a casing that seals the reaction material so as to form a space along an outer peripheral surface of the reaction material. One end of the connection tube is open to the space.