In a robot arm mechanism provided with air intake and discharge ports, the present invention addresses the problem of minimizing effects on workpieces and suitably avoiding situations in which the mechanism sucks the clothing, etc. of a nearby worker. In a robot arm mechanism: a post (2) is supported on a base (1) so as to rotate freely; a crane section (4) is mounted on the post (2) and an extendable arm (5) is supported on the crane section (4) so as to be raised and lowered freely; and the tip of the arm (5) is equipped with a wrist section (6) on which an end effector can be mounted. On the crane section (4), an air intake port (32A) is provided in front, apart from an air discharge port (32B) in the back. In the wrist section (6), an air intake port (34A) is provided on the end closerto the end effector, separated from an air discharge port (34B) on the end that is farther from same.