Test liquid (3) including thermosetting resin is injected from an injection valve (2). Light (L) is irradiated to a spray (6) of the test liquid (3) injected from the injection valve (2) as a treatment for producing a hardening effect to the thermosetting resin. Liquid drops in the spray (6) are hardened and collected as particles. Spray characteristics such as a particle size distribution of the injection valve or the like are analyzed by using the collected particles.