PURPOSE: To obtain decoded data with high quality without the need for reading data again even when consecutive errors are in existence in one frame by replacing a frame having the error with the same data frame of sub channel data.

CONSTITUTION: Digital data are sent from a recording medium 6, a main channel data read circuit 1 reads main channel data, and a sub channel data read circuit 2 reads sub channel data. The read main channel data are delayed by one frame at a delay circuit 4 to make the main channel data synchronize with the sub channel data and the main channel data and the sub channel data synchronous with each other are given to a selection circuit 5. When data of a frame No.4, for example in the main channel data are discriminated to have an error and the result of discrimination is fed via a delay circuit 4a, the selection circuit 5 replaces the No.4 frame data with No.4 sub channel data and the replaced data are outputted.