To provide a trigger coil which can appropriately make a flash arc tube emit light by ensuring electrical insulation between a primary windings and a secondary windings.

A primary winding 2, a core 4 whereon the primary winding 2 is wound, and a secondary winding 3 which is wound on an outer peripheral position of the primary winding 2 to the core 4 are provided. The secondary winding 3 is wound on an outer circumferential surface of a housing 5 which houses the core 4, whereon the primary winding 2 is wound inside. Especially, the core 4 is inserted and disposed inside a bottomed hole constituting a housing part 5s of the housing 5, and the high-voltage terminal 3b of the secondary winding 3 faces the opposite side of the opening part 10 of the housing part 5s, thus enlarging an extended surface distance 12 between it and the primary terminal 2.