To provide a plastic retainer having high positioning precision for a basic member and capable of maintaining high adhesion strength after welding it on the basic member, dispensing with machining on the basic member, and minimizing an impression on a rear surface of the basic member caused by pressing when welding it.

This retainer 1 consists of a holding part 3 holding a clip, a substrate part 5 supporting the holding part, and a pin 6 protruding on the opposite side to the holding part from the substrate part. An engaging part 10 for preventing coming off of the pin 6 inserted into the basic member 2 to which the retainer 1 is attached is formed at a tip of the pin 6. A hole 9 is formed between the substrate part 5 and the root part of the pin 6 in the root part of the pin 6, and the hole 9 forms a storage space for a basic member part when inserting the pin into the fused basic member.