A composition for forming protective films against aqueous hydrogen peroxide solutions, including: a compound of the following formula (1a) or formula (1b) or a compound having a substituent of the following formula (2) and having a molecular weight of 300 or more and less than 800 or a weight-average molecular weight of 300 or more and less than 800; and a solvent, the composition containing the compound of the formula (1a) or formula (1b) of 0.1% by mass to 60% by mass or the compound having the substituent of the formula (2) of 10% by mass to 100% by mass, relative to solids excluding the solvent: (wherein R1 is a C1-4 alkylene or alkenylene group or a direct bond, k is 0 or 1, m is an integer of 1 to 3, and n is an integer of 2 to 4.)