PURPOSE: To enable the extreme miniaturization of a device and also sharp reduction of a manufacturing cost, by using an exciting light source for emitting two types of exciting lights with an approximate wavelength.

CONSTITUTION: A body 20 of the invention detector for luminous material is located in a position corresponding to a conveyance path 15, and a mercury discharge lamp 21, serving as an exciting light source, is situated in a position corresponding to a detecting window 20a in the body 20. Ultrasonic rays with a wavelength of 2,537 based on a discharge energy are radially fed as an exciting light X to the outside by the mercury discharge lamp 21, a fluorescent material 26 at an inner peripheral surface of a bulb 22, simultaneously, is excited by means of the exciting light X, and ultrasonic rays with a wavelength of 3,650 emitted from the fluorescent material 26 are fed as an exciting light Y to the outside togetherwith the exciting light X. This constitution enables the extreme miniaturization of a device configuration and permits the sharp reduction of a manufacturing cost.