A hub transmission with a coaster brake unit includes a hub axle, a drive member rotatably mounted around the hub axle, a hub body rotatably mounted around the hub axle, and a planetary gear mechanism coupled between the drive member and the hub body for communicating rotational force from the drive member to the hub body through multiple rotational force transmission paths. The planetary gear mechanism includes a planet gear supported by a planet gear rack for rotation around the hub axle, and a ring gear engaging the planet gear. The gear rack includes a depression formed in a peripheral direction thereof, and the ring gear includes a serration formed in a peripheral direction thereof. A clutch having an engagement component is movable in a direction of an axis of the axle between a first position, a standby position and a second position. The engagement component engages with the depression in the gear rack for transmitting rotational power to the gear rack when the clutch is located in the first position and the standby position, and the engagement component engages with the serration in the ring gear for transmitting rotational power to the ring gear when the clutch is located in the second position. A biasing mechanism biases the clutch from the second position toward the standby position, and a forcible movement mechanism forcibly moves the clutch from the standby position toward the second position when forward rotational power is applied to the drive member. |