To provide a small-sized flash lamp which is very small to be carried like a key ring and can be used by being easily mounted on fingertips and other devices without using special devices, parts or the like.

The flash lamp comprises a circuit board 10 in which a battery contact point 19 on one side is installed on a lower face of the circuit board 10 while on whose upper face a switching circuit is installed, a plate-formed battery 11 that is laminated and retained by the circuit board so as to put an electrode on one side in contact with the battery contact point, a contact piece 21 which is extended from the circuit board so as to be put in contact with the electrode on the other side of the battery 11, a main body case part 9 which is flatly formed wherein the circuit board, the battery and the contact piece are housed, a light emitter 12 which is arranged at the side of the laminated circuit board and the battery and retained with a light emitting part protruded outside the main body case wherein a lead wire 23 extended from the rear end of the light emitting part is connected to the circuit board, and an operating part 13 which performs the lighting operation of the lithe emitter at the upper or side part of the main body case.