PURPOSE: To perform uniform heating which is safe for a human body by a method wherein, when a body to be treated is provided and heated on a heating plate which is surrounded with a cover, an input/output port for the body to be treated is closed, and the inside of the cover is heated under a thermally exhausted state.

CONSTITUTION: A body to be treated is provided and heated on a heating plate 19 which is surrounded with a cover 28. At this time, an input/output port 29 for the body to be treated is closed. At the same time, the inside of the cover 28 is heated under a heat exhaust condition. Therefore, inflow of outer air into the cover through the input/output port 29 can be prevented. Hot air in the cover 28 does not flow to the outside through the input/output port 29 since a heat exhaust pipe 37 is positively provided. Thus, the safe heating method characterized by the uniform distribution of heating temperature can be obtained.