With no interrupt to a CPU, waveform data stored in a NAND-type flash memory are read out on a page-by-page basis to supply a buffer of a waveform memory with waveform sample data. A series of waveform data are prestored in successive pages of the intermediate buffer capable of high-speed page access thereto. Page number of a page to be read out first is set, and that page is read into a buffer in advance. Before completion of readout of the first page, another page to be read out next is loaded into the buffer. After that, the page number is incremented by one each time readout of one page is completed, and the waveform sample data of the page number continue to be reproduced while being read into the buffer.