A robot hand device comprising: a plurality of finger mechanisms (20, 30, 40, 50) that correspond to an index finger, a middle finger, a ring finger, and a little finger of a human hand, each of which has a first wire for driving (23a, 23b, 33a, 33b, 43a, 43b, 53a, 53b); a plurality of driving parts for bending (70b, 70c, 70d, 70e) that are configured to independently drive the first wire of each finger mechanism so as to bend each of the finger mechanisms; a connecting member (61, 62, 63, 64, 65, 66, 67, 68) that is configured to provide a connection between at least one set of the first wires among a plurality of the first wires; a driving controller that is configured to control the driving of the first wire of each of the finger mechanisms by the driving parts for bending; a second wire (24a, 24b, 34a, 34b, 44a, 44b, 54a, 54b) that is provided on each of the plurality of finger mechanisms and is configured to extend each finger mechanism; and a first driving part for extending that is configured to drive the second wire so as to extend each of the finger mechanisms, characterized in that the first driving part for extending is connected to the second wire of each finger mechanism to drives the second wire of each finger mechanism together, wherein the driving controller is configured to cause the driving part for bending that drives the first wire of the second finger mechanism to assist with the bending operation of the first finger mechanism by transmitting a driving force (F2a) which is a portion of the driving force for the first wire of the second finger mechanism, via the extended connecting member, to the first wire of the first finger mechanism, if a difference between a first posture of the first finger mechanism and a second posture of the second finger mechanism is larger than a predetermined difference when at least the first finger mechanism and the second finger mechanism of the plurality of finger mechanisms bend. a plurality of finger mechanisms (20, 30, 40, 50) that correspond to an index finger, a middle finger, a ring finger, and a little finger of a human hand, each of which has a first wire for driving (23a, 23b, 33a, 33b, 43a, 43b, 53a, 53b); a plurality of driving parts for bending (70b, 70c, 70d, 70e) that are configured to independently drive the first wire of each finger mechanism so as to bend each of the finger mechanisms; a connecting member (61, 62, 63, 64, 65, 66, 67, 68) that is configured to provide a connection between at least one set of the first wires among a plurality of the first wires; a driving controller that is configured to control the driving of the first wire of each of the finger mechanisms by the driving parts for bending; a second wire (24a, 24b, 34a, 34b, 44a, 44b, 54a, 54b) that is provided on each of the plurality of finger mechanisms and is configured to extend each finger mechanism; and a first driving part for extending that is configured to drive the second wire so as to extend each of the finger mechanisms, the first driving part for extending is connected to the second wire of each finger mechanism to drives the second wire of each finger mechanism together, wherein the driving controller is configured to cause the driving part for bending that drives the first wire of the second finger mechanism to assist with the bending operation of the first finger mechanism by transmitting a driving force (F2a) which is a portion of the driving force for the first wire of the second finger mechanism, via the extended connecting member, to the first wire of the first finger mechanism, if a difference between a first posture of the first finger mechanism and a second posture of the second finger mechanism is larger than a predetermined difference when at least the first finger mechanism and the second finger mechanism of the plurality of finger mechanisms bend.