A vane device includes vane units, coupling modules around a shaft body, and connection units. Each coupling member has two brackets each of which has an insertion hole. Each connection unit is disposed between the brackets and has a rotary member, and two pin members threadedly inserted into the rotary member and projecting outwardly from the rotary member to extend into the insertion holes. When the rotary member is rotated, the pin members are moved toward each other so that the pin members are released from the insertion holes, or moved away from each other so that the pin members are respectively inserted into the insertion holes and each connection unit detachably connects one of the vane units to one of the coupling modules.