In a heating device (1002), a scale trapping unit (109) that accommodates an attaching body (7) with superior affinity for scale particles is set in a water circuit (400) including a heat exchanger (108), and the scale particles contained in heated water flowing out from the heat exchanger (108) are caused to attach to the attaching body (7). The attaching body (7) is kept at a high temperature so that the scale particles do not only attach to the surface of the attaching body but also form crystals on the surface of the attaching body. Namely, not only scale particles with a large particle size and large sedimentary properties but also fine scale particles with small sedimentary properties are trapped. During a period where heating is not carried out, tap water is fed from a tap water feed pipe (111) to the scale trapping unit (109) in order to peel the trapped scale from the attaching body (7). The peeled scale is discharged from the water circuit (400) through a scale discharge pipe (112). The trapping ability of the attaching body (7) is thus maintained for a long period of time.