To have the number of data writing increased and to retrieve the next writing position of data at high speed in structuring a ring buffer on a nonvolatile memory.

In a data writing device 1, a ring buffer 2 is constituted on a nonvolatile memory which has the limited number of data writing. Identification information for having a data writing means 4 retrieve a storage place of the previous data is written in each storage area 2a of the ring buffer 2 together with the data and, at the same time, a block pointer BP, which is set on a nonvolatile memory for managing the data by the block unit for putting plural storage areas 2a of the ring buffer 2 together, is made to store a leading position of a block which does not have writing of the data in all the storage areas in a block B completed. An identification information retrieval/write-in position specification means 5 retrieves the next writing position from the block specified by the block pointer BP and the identification information, and indicates a data write means 4 the position concerned.