We performed equation of state measurements of tantalum using laser-induced shock waves. A strong shock wave (> TPa) was generated in tantalum by the direct irradiation of laser beams from the GEKKO⁄HIPER glass laser system (laser wavelength λ_L = 351 nm, laser pulse width τ_L= 2.5 ns) of the ILE of Osaka University. A two-step, two-materials target, called a double-step target, was used in this experiment. The target assembly was fabricated from a base plate (aluminum or copper), a standard step (aluminum or copper), and a sample step (tantalum). The shock velocity was measured directly by observation of the emission from high temperature material or the change of the reflectivity of the rear surface of the target resulting from the arrival of the shock wave. Particle velocity and pressure were calculated using an impedance-matching technique. The obtained EOS data showed close agreement within the limits of experimental error with the extrapolation of the shock compression curve obtained by the conventional experimental shock technique.