PURPOSE: To provide a method for manufacturing a diaphragm unit for obtaining a flat diaphragm film which does not bend nor break and an optical fiber type pressure sensor the pressure sensitive section of which can be increased in size against the size of a sensor head.

CONSTITUTION: A diaphragm unit D is formed by forming a through hole through a spacer 1 and joining a substrate 4 composed of a removing layer 4b and joining layer 4a to one surface of the spacer 1 with the joining layer 4a, and then, removing the removing layer 4b and a diaphragm film 3 is formed on the upper surface of the joining layer 4a or, after forming the through hole through the spacer 1, joining the joining layer 4a of a substrate composed of a diaphragm film layer and the joining layer 4a to one surface of the spacer 1. An optical fiber type pressure sensor is constituted by fixing the end face of an optical fiber to a transparent substrate with the spacer 1 of the diaphragm unit D in between.