To provide a water cleaning apparatus continuously providing a safer and higher water cleaning effect than a conventional one, in rivers and lakes without causing clogging, and a water cleaning method.

This water cleaning apparatus is provided with a sucking means 2 sucking water to be treated from a raw water region such as rivers and lakes; a filter means 3 filtering the water to be treated sucked by the sucking means 2 by a filter medium 3a and biologically treating filtered matter held on the filter medium 3a with organisms; a discharge means 4 for discharging the water to be treated filtered by the filter means 3 and a backwashing means 5 backwashing the filter medium 3a of the filter means 3. Organisms are separated from the filter medium 3a by backwashing by the backwashing means 5 and discharged to the raw water region.