A robot joint structure .alpha. is composed of a metacarpal member 30 and a proximal member 40 swingably connected through a hinge 31 to a side end portion of the metacarpal member 30. The proximal member 40 includes a linear guide device 44 for an MP joint having a moving member movable in association with a self swing motion thereof, and by connecting a rod 32a and the moving member through a link mechanism 50, a driving force of an air-cylinder 32 is transmitted to the proximal member 40. On the other hand, a second robot joint structure .beta. is also provided with linear guide devices 48, 66, 74 and link mechanisms 69, 75, to which a driving force of the air-cylinder 62 is transmitted through a drive shaft 63 in association with a rod 62a. A robot finger is constructed by the first and second robot joint structures. According to such structures, smooth joint motion can be realized, and the robot joint structure and the robot finger having improved gripping force can be provided.