To provide a heat collector of a solar water heater which is simple in structure, has a small number of parts, can inexpensively be manufactured and has high heat collection performance, and to provide a hot water storage tank of the solar water heater which is easy in installation, has high safety and is excellent in aesthetic sense.

One heat collector is constituted as following. A bottom base plate formed of polystyrene foam or the like which is molded with the heat collector room and a flow passage is covered with a resin sheet member and the like. The four circumferential parts of the bottom base plate and the sheet member are supported by a member so as to withstand water pressure. The bottom base plate and the sheet member which are expanded by the water pressure controlled by a beam member. The other heat collector 2 is constituted as followings. A bottom base plate of polystyrene foam or the like which is molded with a heat collector room and a flow passage is covered with the resin sheet member or the like and assembled with an adhesive. At the part of high water pressure, it can be withstood for the water pressure by dispersing the water pressure by setting gluing parts more densely. On the other hand, legs are formed by making a heat insulation container into large raised bottom. When the container is installed on a sloping roof, the inexpensive hot water storage tank 3 which does not need a trestle separately can be made by cutting these legs in desired dimensions.