A new superconductor Sr_1-xLa_xCuO₂, having an infinite-layer structure was prepared in a reductive atmosphere applying high pressure synthesis. Its solid solution limit was around X=0.12. The Tc(onset) value was 43K independently on X and the volume fraction of the superconductor showed a maximum at X=0.10. Positive value was observed on a Hall effect measurement on the sample with X=0.10 in a temperature range above 77K.