To suppress error production for high reliable data and to enable long time recording for data of a low possibility of malfunction by controlling information content written in a unit cell with reference to a sort of data in the case of writing data in a multivalued memory.

An input voice signal is encoded by an encoding means 10, and an information content control means 20 decides information content to be written in one cell with reference to kind of the encoded data, which are written in a multivalued memory 40. Also in the case of reading the data out of the multivalued memory 40, the same information content as was written in is read out of the unit cell and is decoded by a decoding means 30 to obtain an output voice signal. When data of a high possibility or a low possibility of malfunction are written into the device, the information content written into a unit cell of the multivalued memory 40 is decreased for the former (for example, 1 bit per cell) and increased for the latter (for example, 4 bits per cell).