The headline business activity index, known as the Purchasing Managers Index, rose to a 14-month high as output and new orders both showed gains, the research firm said.
By numbers, the PMI rose to 51.3 in May from 49.8 in April.
The dividing line between contraction and growth is 50, so 51.3 shows a slight expansion in Britain's manufacturing sector for the month.
""The UK manufacturing sector had a spring in its step in May, as a brightening domestic market led
to faster growth of out put and new orders. One of the more positive features of the expansion is its
broad-base, with producers of consumer, intermediate and investment goods all reporting
stronger output growth. " said Markit economist Rob Dobson.
Dobson said output was likely to improve in the coming months, "as firms refill warehouses after strong than expected demand has led to a sharp depletion in finished goods stocks."
"The tentative return to job creation in the sector in May also suggests that manufacturers are becoming more confident in the outlook," he said.