A memory accessing method including the following steps is provided. Firstly, two instructions are fetched. Next, the two instructions are respectively decoded to obtain two operation fields and two address fields. The two operation fields indicate the type of operation in accessing the memory. One of the address fields includes a first upper address corresponding to the first memory block and a first lower address corresponding to a first memory unit of the first memory block. The other one of the two address fields includes a second upper address corresponding to the second memory block and a second lower address corresponding to a second memory unit of the second memory block. Then, whether two instructions are performing the same type of operation on the same memory block is determined. If yes, the type of operation indicated by the two operation fields is performed on the corresponding memory block parallelly.