PURPOSE: To obtain a flame detector of miniature size to be able to detect a flame image from different, plurality of zones at the same time, by providing inclinations to more than one sensor ends of optical transmission passage among a plurality of them to the vertical surfaces to the axis of transmission passages.

CONSTITUTION: An optical fiber 35 has a vertical end surface, while the end surface of an optical fiber 36 is ground with a specified angle, and the end of an optical fiber 37 is ground with larger ground angle than that of the end surface of an optical fiber 36. In such a manner, the end surface of each optical fiber has a different ground angle, so that flames from a plurality of zones can be detected at the same time, as a result, accurate flame image can be detected by those optical fibers as a whole. An angle is given to each end surface of an optical fiber by grinding work only, without transforming it by thermoplastic bending, so that transmission loss and scattering in sensing angles can be that transmission loss and scattering in sensing angles can be decreased.