The purchasing managers' index (PMI) came in at 50.1 in April, slightly down from March's 50.2 and below market expectations of 50.3, said the National Bureau of Statistics (NBS) and the China Federation of Logistics and Purchasing.
The index measures changes in activity levels from one month to the next. Anything above 50 signals growth, while anything below that level means contraction.
The sub-index for new orders and new export orders - lead indicators for internal and external demand - weakened to 51.0 and 50.1 respectively.
NBS statistician Zhao Qinghe however said that China's manufacturing activity kept steady growth last month.
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State-run Xinhua news agency quoted Zhao as saying that economy continued to rebound in April because of government's pro-growth measures and supply-side structural reforms.
But analysts worry that recent signs of improvement may be largely-driven by companies and local governments taking on more debt, putting any longer-term recovery in jeopardy.
Prices of raw materials continued the upward trend last month, with the sub-index for purchasing price standing at 57.6, the highest reading in almost two years.
The pace of Chinese growth last year was at its weakest since 1990. The slowdown had prompted the International Monetary Fund to cut its global growth forecasts for China to only 6.3 per cent in 2016.