At present, there are various kinds of locomotion mechanisms of robots such as bipedal locomotion, locomotion on wheels, and meandering. All of these mechanisms need a lot of space. But the locomotion mechanism which needs only a slight amount of space is the peristaltic crawling of earthworms. Moreover, this is more stable than any other locomotion mechanisms. Therefore, we pay attention to the peristaltic crawling of earthworms, which will replace the mechanisms of locomotion on wheels or on foot, aiming to develop an earthworm type robot mobile on unleveled ground, narrow roads, in a heap of rubble, or inside the tubes of nuclear power plants. This paper reports on the characters of pneumatic artificial muscle actuator suggested by us, the design of an experimental peristaltic crawling type robot using the actuators, and their evaluation results.