To provide a printing machine which can prevent ink, water, paper powder, etc., scattering into the printing machine, from adhering to a light emitting part of a recording head and a light receiving part of a light quantity correcting means, while having a simple constitution.

An image recording apparatus 25 is equipped with a recording head 201, a recording head moving mechanism 202, and the light quantity correcting means 300. The recording head 201 is equipped with a light source 251, an optical system lens 252, the light emitting part 253, and an abutting part 254. The means 300 is equipped with a light quantity sensor 301 which has the light receiving part 301a, cover glass 302, a base plate 304, a cylindrical cover 307, and a spring member 308 for urging the cover 307 in the direction of the recording head 201.