PURPOSE: To obtain the light transmission needle for therapy which exactly arrives at the disease root part in a body without pain transmits light to the arrival point to generate heat in a limited narrow range and can be used for obtaining a treating effect by this thermal stimulus.

CONSTITUTION: This constitution and process for production of the light transmission needle for treatment consist in polymerizing a polymerizable compsn. in the hollow part of an extremely fine hollow capillary of a metal to pack a high-molecular material therein and imparting a sharply angled needle tip thereto, thereby giving the extremely fine needle.