Repeated compression test of open-cell type nickel foam (Celmet) was conducted to investigate deformation behavior with changes in density. Cylindrical billets with two pore sizes were compressed up to 90% in nominal strain. Apparent density, buoyant density and dimensions of billets were measured after each compression step. Compressive stress linearly increases without plateau region until the nominal strain of 0.4 with increase in apparent density and with slight increase in diameter. Apparent density and porosity estimated under assumption of no diameter change show good agreement with the experiments. Above the strain of 0.4, the stress as well as diameter apparently increases with remarkable increase in density.