A rotation-adjustable hanging device includes a pivot seat, a hanging arm body and a limiting unit. The hanging arm body includes a pivot end connected pivotally to the pivot seat about a first pivot axis. The limiting unit includes a main body, two limiting arms and two limit ends. The main body is disposed on the pivot seat and defines a second axis. The limiting arms are directed toward the pivot end to extend the limit ends to the arm body such that the limit ends are disposed at two opposite sides of a first line that passes through the first and second pivot axes and such that the limit ends is able to stop rotation of the arm body.