A path generating device 1 has a constraint mid-configuration generator 10. The constraint mid-configuration generator 10 defines a constraint surface in a joint angle space. The path generating device 1 probabilistically generates a mid-configuration in the joint angle space. The constraint mid-configuration generator 10 projects the probabilistically generated mid-configuration onto the constraint surface to generate a projected mid-configuration. Projected mid-configurations generated in this manner are joined to generate a path that does not interfere with any obstacle (environmental object) in a work space.