Falling prices sent another worrying signal about the eurozone economy just before the European Central Bank starts a 1 trillion euro ($1.1 trillion) stimulus effort.
Consumer prices fell 0.6 percent in the 12 months to January, accelerating the 0.2 percent annual drop in December.
Prices are weighed down by the recent plunge in oil prices. But even excluding energy costs, they are weak, a sign of the deep economic malaise afflicting the 19 countries that share the euro currency.
Friday's report by the Eurostat statistics agency showed that the core inflation rate, which strips out volatile food and energy prices, was at plus 0.5 percent, down from 0.7 percent the month before.
