A heating device which transfers heat isothermally to an object to be heated. The heating device includes: a block and a base plate which surround a pipe; a first heat insulating cover which covers an outer periphery of the block and the base plate and forms a first heat insulating layer; and a second heat insulating cover which covers an outer periphery of the first heat insulating cover and forms a second heat insulating layer. The first heat insulating cover includes first heat insulating covers fixed to the block and the base plate respectively. The second heat insulating cover includes second heat insulating covers fixed to each of the first heat insulating covers respectively. The heating device further includes snap locks which detachably fixes the second heat insulating covers.