This paper presents an innovative underactuated wheel module design and analysis for the power wheelchair. The wheel module has two degrees of freedom but uses only one motor so as to make it an underactuated design. A power wheelchair with the wheel modules can move forward as well as sideways, which is needed for disabled people who live in a limited space. Compared to the wheelchair with omni-wheels, this underactuated wheel can definitely be power saving. Kinematic analysis of the power wheelchair with the underactuated wheel modules and some preliminary test results are presented in this paper as well to show its feasibility.