1. A sample analyzing method based on a response obtained upon application of a voltage to a reaction field containing a sample, comprising: a preliminary step for introducing the sample; a first step performed later than the preliminary step for measuring a first response for use in calculation necessary for analyzing the sample; and a second step performed later than the first step for measuring a second response necessary to determine whether a target amount of the sample has been supplied to the reaction field; wherein the application of voltage to the reaction field in the first and the second steps is made by using two electrodes selected from three or more electrodes, and a combination of the two electrodes selected in the first step differs from a combination of the two electrodes selected in the second step.