1. A method for acquiring information on a target object, comprising the steps of: applying a solution containing an Ag ion or an Na ion to the target object; irradiating the target object with an ion beam to ionize the target object after applying the solution; and acquiring information on the mass of the target object that ionizes using time-of-flight secondary ion mass spectrometry after irradiating the target object, wherein the target object that ionizes is either of: (1) an ion corresponding to a mass obtained by addition to a parent molecule of the target object of an Ag ion or an Na ion; or (2) an ion corresponding to a mass obtained by addition to a partial structure of the target object of an Ag ion or an Na ion; wherein the target object is any of: a protein; a peptide; or a metabolite.