The preliminary Markit/Nikkei manufacturing Purchasing Managers' Index (PMI) for Japan declined to 50.2 in February from 52.3 in January.
A reading below 50 indicates contraction of activity, a reading above 50 indicates expansion.
The index was driven by a drop in new orders.
"Production increased at the slowest rate in the current 10-month sequence of expansion, led by a marginal drop in new orders for the first time since June last year. Data suggests that the fall in total new work intakes was caused primarily by a contraction in international demand, with new exports declining at the sharpest rate in three years," economist at Markit, Amy Brownbill, said.