The present invention reduces a melting time without causing an increase in the man-hours for manufacturing a fusible conductor. The present invention is provided with an insulated substrate (11), a heating element (14), an insulating member (15) for covering the heating element (14), a heating element extraction electrode (16) electrically connected to the heating element (14), a first and a second electrode (12), and a fusible conductor (13) connected to the heating element extraction electrode (16) and through to the first and second electrodes (12), the fusible conductor (13) cutting, by melting, a current path between the first electrode (12)(A1) and the second electrode (12)(A2). The fusible conductor (13) is formed in greater thickness than a principal surface part (25), and has a pair of first side edge parts (26) facing each other and a pair of second side edge parts (27) facing each other and formed in lesser thickness than the first side edge parts, the second side edge parts (27) being disposed along the current path extending from the heating element extraction electrode (16) to the first and second electrodes (12).