PURPOSE: To prevent a failure caused by defective contact of a ROM.

CONSTITUTION: A circuit board 20 on which a ROM 22 to be erased is, packaged is mounted on a substrate tray 2 which is housed in a case 1 so as to be drawable. An ultraviolet lamp 11 is arranged facing in parallel with a circuit board main body 21 of the circuit board 20. In order to strengthen the intensity of ultraviolet with which the circuit board 20 is irradiated and uniformalize the intensity distribution of ultraviolet, a reflecting mirror is arranged over the ultraviolet lamp 11. That is, this ROM eraser 100 packaged on the circuit board erases memory signals in the ROM 22 in a state in which it is packaged on the circuit board 20. Therefore, since the ROM can be directly packaged on the circuit board without using a ROM socket, defective contact between the ROM and the ROM socket does not occur.