Omnidirectional mobility is a popular method of moving in narrow spaces. In particular, the planar omnidirectional crawler previously developed by the authors can traverse unstable and uneven terrain with a large contact area. A novel point is that the proposed system is unique in its ability to carry heavy loads in all directions without getting stuck because of the large pressure-receiving area between the crawler and the ground. This work will facilitate omnidirectional motion, which has important implications for the use of robots in spaces such as not only factories, distribution centers, and warehouses but also soft soil in disaster sites. The objective of the present study was to establish a design and control method for an omnidirectional crawler mechanism that can conduct holonomic and two-axis cross-driving. Only two motors are set on the crawler base for translation in the X- and Y-directions, and two large crawler units are arranged for turning. We design a small crawler that has higher traversing ability with a derailment prevention mechanism and tapered track. Further, the relationship between the motor rotational speed as input and crawler velocity as output was verified for control. In addition, it was demonstrated experimentally that the proposed crawler could travel across various types of rough terrain in a target direction.