  We consider the dynamics of power-law inflation with a nonminimally coupled
scalar field $\phi$. It is well known that multiple scalar fields with
exponential potentials $V(\phi)=V_0 {\rm exp}(-\sqrt{16\pi/p m_{\rm pl}^2}
\phi)$ lead to an inflationary solution even if the each scalar field is not
capable to sustain inflation. In this paper, we show that inflation can be
assisted even in the one-field case by the effect of nonminimal coupling. When
$\xi$ is positive, since an effective potential which arises by a conformal
transformation becomes flatter compared with the case of $\xi=0$ for $\phi>0$,
we have an inflationary solution even when the universe evolves as
non-inflationary in the minimally coupled case. For the negative $\xi$, the
assisted inflation can take place when $\phi$ evolves in the region of $\phi<0$
\.
