1. A latent-image measuring device that measures an electrostatic latent image formed on a sample, the latent-image measuring device comprising: an emitting unit that emits a charged-particle beam to the sample; a detecting unit that detects a charged-particle signal obtained through emission of the charged-particle beam; a charge-distribution measuring unit that measures charge distribution on the sample; and an optical system that exposes the sample a plurality of times to form the electrostatic latent image on the sample.