  We investigate a trajectory for the Wilson flow in the theory space. For this
purpose, we determine the coefficient of the plaquette and rectangular terms in
the action for the configurations defined by the solution of the Wilson flow.
The demon method regarded as one of the inverse Monte Carlo methods is used for
the determination of them. Starting from the conventional Wilson plaquette
action of quenched QCD, we find that the coefficient of the plaquette grows
while that of the rectangular tends to negative with the development of the
flow as the known improved actions. We also find that the trajectory forms a
straight line in the two-coupling theory space.
