Provided is an antireflection film having excellent abrasion resistance.In the antireflection film, a hydrogenated carbon film as a first layer is formed on a surface of an optical substrate. A MgF2 film as a second layer having a lower refractive index than the first layer is formed on the first layer. Likewise, a third layer formed of the hydrogenated carbon film, a fourth layer formed of the MgF2 film, and a fifth layer formed of the hydrogenated carbon film are formed. During the formation of the hydrogenated carbon film, a mixed gas of argon and hydrogen is supplied to a vacuum chamber such that some of C—C bonds in the film are replaced with C—H bonds. Due to the C—H bonds, an antireflection film having excellent abrasion resistance and adhesiveness and having a low refractive index can be obtained.