The objective of this research is to analyze humanoid's jumping and landing motions on a view point of arms' dynamical coupling onto jumping. Humans seem to use arms' swinging for walking or running effectively and jump highly by swinging up arms high. So, we gave input torques to arms in such a way as to swing arms similar to humans, and changed timing to start swinging them, comparing them with humanoid's motion that does not swing the arms through numerical simulation. Then we have confirmed that appropriate swinging motions of arms help the jumping to be higher than those without arms' swinging.