Abstract: In this invention, there is provided a magnetic disk apparatus and a command processing method of the magnetic disk apparatus in which the cache function can be effectively performed even in a case where read commands and write commands are alternately issued and the read or write command can be executed at high speed. An HDC includes a read address holding register in which an access starting address is set when a read command is issued from a host system and which holds an access address associated with the read command and a write address holding register in which an access starting address is set when a write command is issued from the host system and which holds an access address associated with the write command.