In order to enable humanoids to walk steadily, it is important to use various walking forms. For examples, humanoids should walk not in biped but in quadruped when the ground is rough or they cannot believe that the space before them is and will be clear. With having choices of walking forms, they can access wider area by therselves. In this paper, we propose a way to extend a conventional biped walking pattern generator to a generalized walking pattern generator under arm/leg coordination by forcusing on gait pattern and the way to calculate target ZMP trajectory, and conduct a walking experiment over uneven ground by switching a walking form from biped to quadruped. Also we propose an attitude stabilization control system for walking over rougher ground and conduct a simple test for its validation.