To provide an exposure unit which can be assembled with high accuracy.

A reference surface to guide a base material side of a printing paper to a reference plate 51 formed of a plate and a plurality of openings 51A with a transfer roller passing therethrough are formed. The reference plate 51 is connected and fixed to a supporting part Fa formed on a frame F in a positioned state via a parallel pin 72, and the frame F supports the transfer roller and a press roller.