The display controller (1) includes: a DRAM (31); a SRAM (32) which consumes electric power less than the DRAM (31); an update judging section (61); a secondary compression section (70); and a decompression section (40). In a case where the update judging section (61) has judged that image data is not updated, (i) the secondary compression section (70) compresses image data and then stores compressed image data in the SRAM (32), (ii) the DRAM (31) stops a memory retaining operation, and (iii) the decompression section (40) decompresses the compressed image data and then supplies decompressed data to an LCD (3).