An electric apparatus (20; 40; 60) having a heat generating function, wherein the electric apparatus is a water boiler that can boil water or a coffee maker that can extract coffee by use of the heat generating function, wherein the electric apparatus is configured to use as a power source a battery pack (B1, B2) having a plurality of cells inside a battery case and which battery pack (B1, B2) is configured to be used in an electric power tool, wherein electric power of the battery pack (B1, B2) is used for the heat generating function, wherein the electric apparatus is configured such that a plurality of battery packs (B1, B2) can be used in the electric apparatus, wherein the plurality of battery packs (B1, B2) comprises a first battery pack and a second battery pack, the first and second battery pack (B1, B2) having different rated voltages, wherein the electric apparatus is configured such that the plurality of the battery packs (B1, B2) can be electrically connected to the electric apparatus in parallel, and the battery packs (B1, B2) can be switched to supply power to the electric apparatus, the electric apparatus includes a first battery-attaching part (25a; 43a) that is used for removably attaching the first battery pack and a second battery-attaching part (25b; 43b) that is used for removably attaching the second battery pack, and the first battery pack (B 1) and the second battery pack are configured to be removably attached to the first battery-attaching part (25a; 43a) and the second battery-attaching part (25b; 43b), respectively, by sliding the first and second battery packs (B1, B2) to the electric apparatus (20; 40; 60). wherein the electric apparatus is a water boiler that can boil water or a coffee maker that can extract coffee by use of the heat generating function, wherein the electric apparatus is configured to use as a power source a battery pack (B1, B2) having a plurality of cells inside a battery case and which battery pack (B1, B2) is configured to be used in an electric power tool, wherein electric power of the battery pack (B1, B2) is used for the heat generating function, wherein the electric apparatus is configured such that a plurality of battery packs (B1, B2) can be used in the electric apparatus, wherein the plurality of battery packs (B1, B2) comprises a first battery pack and a second battery pack, the first and second battery pack (B1, B2) having different rated voltages, wherein the electric apparatus is configured such that the plurality of the battery packs (B1, B2) can be electrically connected to the electric apparatus in parallel, and the battery packs (B1, B2) can be switched to supply power to the electric apparatus, the electric apparatus includes a first battery-attaching part (25a; 43a) that is used for removably attaching the first battery pack and a second battery-attaching part (25b; 43b) that is used for removably attaching the second battery pack, and the first battery pack (B 1) and the second battery pack are configured to be removably attached to the first battery-attaching part (25a; 43a) and the second battery-attaching part (25b; 43b), respectively, by sliding the first and second battery packs (B1, B2) to the electric apparatus (20; 40; 60).