Robot hand mechanism

A robot hand mechanism comprising:

• a main portion corresponding to a portion other than a thumb of a hand;
• a thumb portion corresponding to the thumb;
• a first rotation shaft that is parallel to a second direction perpendicular to a first direction in which the main portion extends and that flexes and extends the main portion in a first rotation direction;
• a second rotation shaft that is parallel to the first rotation shaft and that flexes and extends the main portion in the first rotation direction;
• and
• a third rotation shaft that is parallel to the first direction or inclined in an oblique direction with respect to the first direction about a third direction perpendicular to the first direction and the second direction and that rotates the thumb portion in a second rotation direction with respect to the main portion, wherein
• in a state in which the main portion is extended, the first to third rotation shafts are arranged on a same plane.