The mechanism of L - H transition and transport barrier formation is studied by the use of a one-dimensional transport code including plasma rotation and radial electric field. Particle transport simulation with a fixed temperature profile has indicated that the density profile is quite sensitive to the edge plasma temperature. When the edge temperature exceeds a critical value of about 100 eV, the radial electric field is built up near the plasma edge and the rotation shear reduces the particle transport. The large density gradient due to the reduction of transport enhances the bootstrap current which also contributes to the reduction through less magnetic shear.