Around 26,000 households have lost power, authorities added.
“The typhoon is pretty solid and its impact is most obvious today bringing strong winds, rains and waves before it gradually moves away tomorrow,” said forecaster Hsu Chung-yi.
At 0200 GMT, Chanthu was 90 kilometres (56 miles) northeast of Hualien, packing gusts of up to 198 kilometres an hour, the bureau said.
Most businesses and public venues were closed in eastern and parts of northern Taiwan, including the capital Taipei where heavy rains started on Sunday.
Around 2,600 people in landslide-prone areas around Hualien have been evacuated while some 31,000 troops are on standby for relief work.
Taiwan is regularly hit by tropical storms in the summer months.
In a rare exception to the rule, not a single typhoon made landfall last year, the first time in 56 years.
That helped fuel the worst drought in decades until heavy rains set in a few months ago and brought needed relief.