A mounting structure is provided which comprises a plurality of seat parts that are formed on a peripheral edge part of an anti-fog sheet covering an inner face of a shield, a plurality of support holes that are provided in the shield at positions corresponding to the seat parts, and a plurality of retaining members that retain the anti-fog sheet by being seated on the seat parts while being supported by the support holes, wherein the retaining member (10) is formed as a single component from a synthetic resin, the single component comprising a main shaft (11) that has at one end a head portion (11a) abutting against an outer face of the shield (3) and is rotatably fitted into the support hole (8), an eccentric shaft (12) that is connectedly provided eccentrically with the other end of the main shaft (11), can be seated on the seat part (7), and has a small diameter, and an expanded end part (13) that is connectedly provided with the other end of the eccentric shaft (12) and can pass through the support hole (8), and the main shaft (11) is provided with an elastic deformation part (17, 19). Thus, it is possible to obtain a structure for mounting an anti-fog sheet to a shield in which a retaining member will not break even when a shield receives a load, and the retaining member is formed from a single component, is therefore inexpensive, and is easy to handle.