A time-of-flight mass spectrometric apparatus was built for infrared matrix-assisted laser desorption/ionization (IR-MALDI) experiments using a free-electron laser (FEL). Preliminary experiments were carried out with a CO₂ laser at 9.5 μm and a FEL at 10.6 μm. These mid-IR wavelengths were shown to produce light atomic ions from solid samples. The detected ion peaks were broadened by the FEL macropulse with 15 μs width. Applying a delayed extraction pulse to FEL-generated ions brought about a small improvement on the mass resolution. By chopping a flux of ions at exit of the ion source region, the ion peak width became narrower by a factor of more than 10.