To provide a data encoding circuit capable of securing real-timeness of a recording operation even in a memory of a low operation clock frequency by reducing the number of times of accessing the memory, and simultaneously reducing power consumption and memory costs. Prior to its writing in a memory (101), data from a host is input to an EDC arithmetic operation circuit (110) and a scrambling arithmetic operation circuit (111) to be processed, and then the error correction codes are added to the data written in the memory (101) from the scrambling arithmetic operation circuit (111) by a PI arithmetic operation circuit (104) and a PO arithmetic operation circuit (105). Accordingly, it is possible to omit memory access when the data is written from the host in the memory, and memory access when the data is read from the memory to the EDC arithmetic operation circuit. Thus, it is possible to reduce an operation clock frequency of the memory (101).