A high efficiency roll-type electret polypropylene (PP) filter with an external electric field was developed and its particle collection efficiency and air cleaning capacity was investigated in a room when applied to an air cleaner having a fan. To enhance air cleaning performance of the cleaner, a wire-plate type ionizer was installed in front of the filter to enhance electric field to filter and one side of the filter was embossed by press of a pattern with a lot of circular projection. Performance test results showed that the newly developed electret PP filter with an ionizer becomes an appropriate filter to be applied to indoor air cleaner due to its low pressure drop and high air cleaning performance.