A shaft member is provided for a human-powered vehicle. The shaft member is configured to be attachable to a body of the human-powered vehicle in a manner restricting rotation relative to the body. The shaft member includes a setting surface on which a plurality of strain gauges are arrangeable. The setting surface includes a plurality of setting portions configured to allow for arrangement of one or more of the strain gauges. The setting portions are provided in the setting surface at different positions in a circumferential direction of the shaft member.