The magnetic field dependence of filling factors has been investigated on InP based In053Ga047As/In052Al048As quantum well samples with two occupied subbands by means of magnetotransport measurements at the temperature of 15K in a magnetic field range of 0 to 13T. Under the condiction that Laundau-level broadening is larger than the spin splitting of each subband, filling factors are even when the splitting energy of two subbands is an integer multiple of the cyclotron energy, i.e.ΔE21=kωc. If the splitting energy of two subbands is half of an odd interger multiple of the cyclotron erergy, i.e.ΔE21=(2k+1)ωc/2, the filling factor is odd.