Analysts had expected the improvement to -7.1. Eurozone business confidence was also up, to 0.37 from 0.30 in April. The rise suggests that the economic recovery may gather some pace in the second quarter.
Manufacturing and services balances also strengthened, with the latter pointing to increases in annual output of 1.5 per cent. However, France's Economic Sentiment Indicator (ESI) weakened again, suggesting flatlining GDP growth.
"Overall, the Eurozone recovery is still not strong enough to make a significant dent in high unemployment or ward off deflationary pressures", said James Howat, European economist at Capital Economics.