A thin battery powered lighter, which has superior portability and usable as an advertising medium, is provided. The lighter includes a thin flat case (2); a sheet type battery (3) provided within the case (2); a heating element (4) connected to the battery (3); and a power switch (5) for establishing an electrical connection between the battery (3) and the heating element (4). The case (2) includes a slide member (6) for opening and closing an ignition window (21), which is provided at a position that the heating element faces (4), and an operating button (51) for operating the power switch (5). When the ignition window (21) is closed by the slide member (6), a portion of the slide member is interposed between contact points of the switch, precluding an operation of the operating button (51). The electrical connection is enabled by operating the operating button (51) in a state in which the ignition window (21) is open.