The volcano spewed ash and gravel that flew as far as 200km away, officials said.
The BBC's Alice Budisatrijo in Jakarta says thick dust in villages close the volcano makes it dangerous for pedestrians and vehicles to be on the road.
Mount Kelud, which had been rumbling for several weeks, erupted on Thursday evening.
Officials said on Friday that the eruption was gradually subsiding.
Experts say the volcano tends to quieten down after a large eruption, and more big eruptions are unlikely.
The volcano last erupted in 1990, killing dozens of people. A powerful eruption in 1919 killed around 5,000 people.
Indonesia lies across a series of geological fault-lines and is prone to frequent earthquakes and volcanic eruptions.
There are about 130 active volcanoes in Indonesia.
Earlier this month, Mount Sinabung on the island of Sumatra erupted, killing at least 14 people.
Are you in Java? How have you been affected by the eruption of the volcano? Send your stories to Haveyoursay@bbc.co.uk with the heading Java.