Provided is an optical fiber connection method for using an optical fiber connector which includes a mechanical splice designed to connect a first optical fiber having a coating diameter D to mechanically connect two optical fibers that include a second optical fiber having a coating diameter d smaller than the coating diameter D. This method includes a first step of inserting the second optical fiber into a tube (30) to obtain a tubed optical fiber (31); a second step of fixing the tubed optical fiber (31) in a fiber holder (15); a third step of inserting the tubed optical fiber (31) into the mechanical splice (2) and placing distal ends of the two optical fibers including the tubed optical fiber (31) end to end; and a fourth step of fixing the tubed optical fiber (31) in the mechanical splice (2) in a state in which the distal ends of the two optical fibers are placed end to end.