We study trajectory generation and attitude control of a two-dimensional space robot floating in space. The conservation law of angular momentum leads to nonholonomic constraints and hence results in inducing the so-called geometric phase of the base motion, while from the view point of attitude control of space robots, we need to control the attitude of space robots with no phase. To do so, we develop equations of motion of a two-dimensional space robot in the context of regular Lagrangian systems with holonomic kinematic constraints and we propose a trajectory planning of a space robot with controlling the base attitude.