In the related art, a configuration is known in which an ISOFIX anchor as an attachment tool for fixing a child seat is provided in a rear seat surface of a vehicle seat (JP-A-2015-085730). The ISOFIX anchor is provided in the state of being embedded in a hole which is formed though a portion formed in a rear end portion of a seat cushion and bulging in a bank shape. The embedded hole of the ISOFIX anchor is normally configured such that a front-side opening is covered with a cover member which is openable and closable. When the child seat is mounted, the cover member is opened so that the ISOFIX anchor therein is exposed to a front side.
In the above-described related art, the child seat is slid to be pushed in the hole in a state where the cover member is opened, thereby maintaining a position of the cover member in a state where the hole is opened. However, with such a configuration, a space for accepting the cover member in the hole, and a mechanism which maintains the cover member in the hole in an opened posture are provided necessarily, and the hole is increased in size and is complicated.