Taiwan said China launched 11 ballistic missiles into waters around Taiwan's north-east and south-west coasts.
Japan said five Chinese missiles landed in its waters as well, calling for an "immediate stop" to the exercises.
China saw the visit, by the US house speaker Mrs Pelosi, as a challenge to its claims of sovereignty over Taiwan.
It sees Taiwan as a breakaway province that will eventually be brought under its control - by force if necessary.
The US, for its part, does not officially recognise Taiwan, which has for all practical purposes been independent since 1950. However, Washington maintains a strong relationship with the island - which includes selling weapons for Taiwan to defend itself.