This is the lowest score since late 2016 and indicates a reduced pace of growth – any score of above 50 shows an expansion taking place.
The manufacturing and services sectors both slowed, with the dip led by the biggest economies, Germany and France.
“While the surveys from February through to April had seen widespread cases of business activity being disturbed by temporary factors such as bad weather, strikes, illness and the timing of Easter, the May survey saw frequent reports of business being disrupted by a higher than usual number of public holidays, which workers often bridged on to weekends,” said IHS Markit.
Businesses also reported shortages of raw materials and workers.
Economists said there are few signs of any pickup in growth in the months ahead either.