  We have investigated the magnetism and the superconductivity of an
electron-doped Pr$_{1-x}$LaCe$_{x}$CuO$_{4}$ (PLCCO) using single crystal and
powder samples by means of zero-field muon spin rotation/relaxation
(ZF-$\mu$SR) and magnetic susceptibility measurements. Muon spin rotation
corresponding to antiferromagnetic (AF) order was observed in the sample with
0.04$\leq${\it x}$\leq$0.11. Changes in magnetic properties of Cu spins upon Ce
doping were revealed because the effect of the rare earth moment was
negligible. Bulk superconductivity was identified in a wide Ce concentration
range of 0.09$\leq${\it x}$\leq$0.20 with a maximum transition temperature of
26 K. At low temperatures, the superconducting (SC) phase abruptly appears by
doping with linking quick destroy of the AF ordered phase at {\it x}$\sim$0.09,
indicating the competitive relation between two phases.
