Effects of presence of phosphorus on the hydrogen desorption kinetics from SiH4/Si (100) surface has been investigated by H-2-temperature-programmed-desorption (TPD) measurements. The beta(1)-TPD peak shifted toward higher temperatures by about 10 degrees C when phosphorus was predeposited to theta(p) = 0.25 ML, and the shift increased with decreasing SiH4 exposure. Two analyses, the Arrhenius plot and the order plot, have been applied to the TPD spectra, clarifying that the 0.25 ML phosphorus on clean Si (100) surface suppresses the hydrogen desorption by increasing both the activation energy from 2.0+/-0.2 to 2.5+/-0.1 eV and the reaction order from 1.0+/-0.2 to 2.0+/-0.2.