Spin dependent transport was investigated in lateral $Py(Ni_{81}Fe_{19})/Au/Py$ spin valve devices. Clear spin valve effect was observed in conventional four-terminal measurement geometry. Higher resistance was found in antiparallel magnetization field of two Py electrodes which is determined by anisotropy magnetoresistance (AMR) measurements. The rectangular shape of spin signal together with good agreement of switching field convinces observed spin valve signal is resulted from effective spin injection and detection. The magnetoresistance ratio decays exponentially with channel length by which spin diffusion length of Au channel was estimated to be 76 nm.