An apparatus for measuring PVT properties of hydrogen was developed on the basis of the isochoric method in the temperature range from 473 K to 773 K and at pressures up to 100 MPa. Due to very low hydrogen density, it is difficult to measure the mass of sample in the sample cell (250 cc) accurately, and hence an expansion cell with a large volume (2500 cc) was equipped to combine with the gas expansion method to determine the initial densities of the isochors. To confirm the validity of this apparatus, nitrogen was first measured from 473 K to 773 K and up to 100 MPa. The obtained data are in good agreement with a reference equation of state for nitrogen within 0.1 %. Finally, we measured the PVT properties of hydrogen at 473 K and up to 100 MPa. The present data agree with the data obtained by the Burnett method within 0.1 %.