  We report observation of the supernova remnant IC443 (G189.1+3.0) with the
Fermi Gamma-ray Space Telescope Large Area Telescope (LAT) in the energy band
between 200MeV and 50GeV. IC443 is a shell-type supernova remnant with mixed
morphology located off the outer Galactic plane where high-energy emission has
been detected in the X-ray, GeV and TeV gamma-ray bands. Past observations
suggest IC443 has been interacting with surrounding interstellar matter.
Proximity between dense shocked molecular clouds and GeV-TeV gamma-ray emission
regions detected by EGRET, MAGIC and VERITAS suggests an interpretation that
cosmic-ray (CR) particles are accelerated by the SNR. With the high gamma-ray
statistics and broad energy coverage provided by the LAT, we accurately
characterize the gamma-ray emission produced by the CRs accelerated at IC443.
The emission region is extended in the energy band with theta_68 = 0.27 deg +/-
0.01 deg (stat) +/- 0.03 deg (sys) for an assumed 2-dimensional Gaussian
profile and overlaps almost completely with the extended source region of
VERITAS. Its centroid is displaced significantly from the known pulsar wind
nebula (PWN) which suggests the PWN is not the major contributor in the present
energy band. The observed spectrum changes its power-law slope continuously and
continues smoothly to the MAGIC and VERITAS data points. The combined gamma-ray
spectrum (200MeV <E< 2TeV) is reproduced well by decays of neutral pions
produced by a broken power-law proton spectrum with a break around 70GeV.
