A print-document conversion apparatus includes a conversion-module activation section that activates, as a process, a conversion module for performing conversion processing for converting print-document data which is described in a page description language and which includes units of processing into print-image data. The conversion module includes a thread activation part, an assigning part, and a shared cache. The thread activation part activates conversion processing threads. The assigning part assigns the units of processing to the conversion processing threads, and causes the conversion processing threads to perform processing on the units of processing. The shared cache is shared by the conversion processing threads. When a conversion result obtained by converting an object included in the units of processing is stored in the shared cache, each of the conversion processing threads obtains the stored conversion result instead of obtaining the conversion result by converting the object.