Searching for single electron tunnelling (SET) oscillations has been done in single ultrasmall Josephson junctions of area S≈0.01 μm2 at low temperatures, T≈50 mK. The current-biased regime of the junctions was achieved by insertion of high-Ohmic metallic resistors with R≈500 kΩ into dc leads and additional tunnel junctions of the same area into the voltage leads. Existence of the SET oscillations was proved by observation of the peaks in the dV/dI curves under irradiation of the junctions by an external RF signal when the critical current was suppressed by a magnetic field. The dc current position of the peaks was proportional to the frequency of the RF signal, following a relation I=±ef in correspondence to predictions of the Orthodox theory. Without magnetic field, clear peaks occurred at I=±2ef, following the Bloch relation.