A drawing apparatus which can create an exposure pattern rapidly. The drawing apparatus has a raster conversion processing module for converting vector images as wiring patterns into bitmap image data, an image cache module for temporarily storing a predetermined-size cached image supplied from the raster conversion processing module, a first compression module for compressing the cached image stored in the image cache module, a second compression module for compressing the cached image stored in the image cache module in a compression ratio differing from that of the first compression module, a comparison module for comparing data sizes of compressed data generated by the first and second compression modules and selecting one having a smaller data size, a memory access module for writing the compressed data selected by the comparison module, into a storage module, and a cache region control module for controlling a compression status of the cached image.