A memory management device, an image forming apparatus, and an image forming method include an OS-management-memory-region managing unit configured to divide a physical memory space into a management region managed by an OS and a non-management region that is not managed by the OS, assign the management region to the virtual memory space, and acquire and/or free a memory space of the management region. The image forming apparatus includes an OS-non-management-memory-region managing unit assigning the non-management region to the virtual memory space so that an application program acquires and/or frees a memory space of the non-management region. The OS-management-memory-region managing unit includes a window region provided so that the OS refers to the non-management region. Data is read and/or written from and/or into the OS-non-management region via the window region.