  We report the discovery of energy-dependent morphology for the GeV gamma-ray
emission from HESS J1857+026 with more than 13 years of {\it Fermi} Large Area
Telescope (LAT) data. The GeV gamma-ray emission from this region is composed
of two extended components. The hard component with an index of $1.74 \pm 0.07$
in the energy range of 0.5-500 GeV is spatially coincident with HESS J1857+026,
and its 68\% containment radius varies from $\sim 0.44^\circ$ below 40 GeV to
$\sim 0.30^\circ$ above 140 GeV. The hard GeV gamma-ray spectrum and the
energy-dependent morphology of HESS J1857+026 make it favor a PWN origin, which
is associated with the energetic pulsar, PSR J1856+0245. The soft component
with an index of $2.70 \pm 0.16$ and another extended gamma-ray source detected
in this region, 4FGL J1857.9+0313e with an index of $2.55 \pm 0.07$, are
spatially coincidence with two molecular clumps in the northeast and southwest
of HESS J1857+026, which favors the hadronic process, and the protons could be
accelerated by the hypothetical SNR associated with PSR J1856+0245.
