Recently, as the advances of ICT, many people use a cloud service. Furthermore, searchable encryption schemes begin to be used in the cloud from the security perspective. However, most of these have the risk of frequency analysis. We propose a new method that keep a search keyword secret against frequency analysis by using false positive which is one of the features of Bloom filter. This method makes mapping of the keyword difficult by false positive rate which is higher than usual. Furthermore, it is able to search data correctly more than 99.9%.