To provide a joint device for requiring a shorter distance from a turning center to a connection portion of a member when turnably connecting members to each other.

A joint block 4 is housed between a first bearing 6a and a second bearing 6b, and a shaft 12 is inserted sideways through the joint block 4. A hexagonal socket head button bolt 2 is inserted upward through the shaft 12 and the joint block 4, and its front end 2b is connected directly to a socket holder 20. This requires a shorter distance H between the connection portion to the socket holder 20 mounted on a stump portion and the turning center of the shaft 12 (an elbow). When a person whose upper arm has a longer stump wears an artificial arm, positions of right and left elbows correspond to each other.