Abstract: An oscillating mechanism for a spinning reel that moves a spool shaft in a spool shaft direction in conjunction with a rotation of a handle shaft includes a sliding gear, a cam gear and a slider. The sliding gear rotates in conjunction with the rotation of the handle shaft. The cam gear has a gear portion formed from metal that includes a gear body configured to mesh with the sliding gear and a boss protruding from the gear body, and a resin support portion supporting a radially inward side of the gear portion and configured to rotate integrally with the gear portion. The slider is mounted on the spool shaft and includes an engagement groove in which the boss is configured to engage and which is configured to move the spool shaft in the spool shaft direction by moving the boss along the engagement groove.