The metamagnetic behaviour, which corresponds to one of the characteristic properties in the heavy fermion compounds, was studied by measuring the electrical resistivity under pressure and magnetic field for a typical heavy fermion compound CeCu6 with orthorhombic structure. The transverse magnetoresistance at 100 mK indicated a peak structure at H-m = 20 kOe for the magnetic field H//c-axis under ambient pressure. H-m is found to increase linearly as a function of pressure and indicates H-m = 102 kOe at 1.75 GPa, for example. The quantum critical point is thus likely to exist at a slightly negative pressure value of similar to 0.21 GPa from extrapolating H-m to zero. The rho(0) and A values in the electrical resistivity rho = rho(0) + AT(2) decrease steeply in magnitude with increasing pressure and magnetic field, indicating that the heavy fermion state is destroyed by pressure and magnetic field.