  In considering a social network, there are cases where people is transferred
to another place. Then the physical (direct) relations among nodes are lost by
the movement. In terms of a network theory, some nodes break the present
connections with neighboring nodes, move and there build new connections of
nodes. For simplicity we here consider only that two nodes exchange the place
each other on a network. Such exchange is assumed to be constantly carried out.
We study this dynamic network (node exchange network NEN) and uncover some new
features which usual networks do not contain. We mainly consider average path
length and the diameter. Lastly we consider a propagation of one virus on the
network by a computer simulation. They are compared to other networks
investigated hitherto. The relation to a scale free network is also discussed.
