To realize a recorder which can write event information simultaneously to a memory and can utilize the event information as trigger information when data are to be reproduced.

The waveform recorder is provided with an A/D converter for sampling and digitally converting waveform signals to be recorded, a trigger detector to which outputs of the A/D converter are inputted, a memory controller for writing outputs of the A/D converter to the memory by a mode set by a CPU upon receipt of outputs of the trigger detector, and a display controller for outputting memory contents to a display via the memory controller. A latch means for latching event data inputted by the operator synchronously with the sampling is set to the waveform recorder. The memory controller writes contents of the latch means together with outputs of the A/D converter to the memory.