PURPOSE: To provide the optical parts having small double refractions and the high adhesion of an antireflection film by providing the surface of a base material consisting of a resin specified in plural structural units with the antireflection film.

CONSTITUTION: The surface of the base material consisting of the resin which consists of the structural units I to III respectively expressed by formula II to formula III and in which the molar fraction x of the structural unit I is substantially equal to the total molar fraction y+z of the molar fraction y of the structural unit II and the molar fraction z of the structural unit III is provided with the antireflection film. In the formulas, n is 0, 1 or 2; A is ≤20C bivalent satd. aliphat hydrocarbon group, satd. alicyclic hydrocarbon group or arom. hydrocarbon group. The molar fraction x of the structural unit I expressed by the formula I is approximately ≤50mol.% and the molar fraction y of the structural unit II expressed by the formula II is in a ≤50mol.% range and more preferably ≥40mol.% and ≥50mol.%. The preferable molar fraction z of the structural unit III is ≥1mol.% and ≤20mol.%.