Hydrogen at high pressure in the fluid state is of great interest for understanding interiors of gas giant planets. We newly obtained Hugoniot data for liquid hydrogen up to 55 GPa under laser-driven shock loading using impedance matching to a quartz standard. The shocked temperature was determined simultaneously from the brightness temperature. The compression and temperature are almost consistent with theoretical models. High reflectivity of hydrogen was observed at 40 GPa, which suggests the fluid becomes conducting.