We report the measurements of superconducting properties of Y–Ba–Cu–O compound, particularly the critical current and the gap structure. X-ray diffraction shows that the sample has strong c-axis orientation perpendicular to the pressed surface of bulk material. Temperature dependence of critical current is found to be in good agreement with the Ginzburg-Landau theory near T=Tc. Single particle tunneling between a sintered bulk Y–Ba–Cu–O compound and a Pb film yields a series of gap structures. The observed value of 2Δ/kBTc at low temperatures is about 10 when Δ is estimated at the gap bump voltage and 6–7 when estimated at the point where superconducting and normal tunnel resistances become equal. It is pointed out that the latter method does not apply in the case of d-wave superconductors even at T = 0.