Provided is a harness bending regulation member to be attached to a flexible harness protective tube, including: a high rigid unbendable portion into which an electric wire is inserted; and a bendable portion projecting in an axial direction of the unbendable portion from a tip end of one side of the unbendable portion, the bendable portion regulating a bending of the harness protective tube in a curved shape. The harness protective tube is routed from an oscillating member on a side close to a fixing structure to another oscillating member closer to a slide structure, the harness bending regulation member is placed inside of a harness holding tube on the side of the fixing structure, and the bendable portion is placed toward the slide structure along an inner surface of the harness protective tube.