An address translation buffer of a processor including a memory unit that has a first area with first entries storing first address translation pairs of a virtual address and a physical address corresponding to the virtual address, each of the first address translation pairs is subjected to a index tag which is a part of the virtual address, and a second area with second entries storing second address translation pairs, each of the second address translation pairs is subjected to a whole part of the virtual address, and a search unit that searches the first area for an address translation pair by using a index tag included in a virtual address to be translated, and searches the second area for the address translation pair by using a whole part of the virtual address when the address translation pair is not found in the first area.