PURPOSE: To provide production of single mode evanescent wave photocoupler with which wavelength dependence is decreased by using two optical fibers equalized at the beginning.

CONSTITUTION: This production is provided with a process for preparing 1st and 2nd single mode optical fibers 10, having the practically equal propagation constant, heating process for heating the 1st optical fiber 10 along the 1st lengthwise segment of the 1st optical fiber 10, while pulling the 1st optical fiber 10 in order to decrease the diameter of 1st lengthwise segment of the 1st optical fiber 10, so as to provide the practically equal diameter dimension, holding process for mutually holding in parallel the 1st and 2nd optical fibers 10 at one part of the 1st lengthwise segment, and process for forming a coupling area by mutually fusing the held in parallel parts of the 1st and 2nd optical fibers 10.