A retractable half-body sauna device includes a main body, a retractable body, a first sliding member, and a second sliding member. The first sliding member is installed along inner surfaces of the bottom plate, the two side plates, or the bottom plate and the two side plates of the main body. The second sliding member is installed along outer surfaces of the bottom plate, the two side plates, or the bottom plate and the two side plates of the retractable body. The first and second sliding members are configured for engaging and sliding on each other so as to the retractable body is pulled partially out of and pushed partially into the main body, such that an inner space defined by the main body and the retractable body gets maximized and minimized, respectively.
