A hub assembly for a bicycle includes a shaft, a hub body rotatably mounted on the shaft, a drive seat rotatably mounted on the shaft and engaging the hub body, a first bearing located between the shaft and the hub body, a second bearing located between the shaft and the hub body, and a bushing unit located between the first bearing and the second bearing. The bushing unit includes a first adjusting sleeve and a second adjusting sleeve. The first adjusting sleeve has a first end provided with an outer threaded portion and a second end abutting the first bearing. The second adjusting sleeve has a first end provided with an inner threaded portion screwed onto the outer threaded portion of the first adjusting sleeve and a second end abutting the second bearing.