A particle detecting device includes: a storing device that stores first boundary information wherein the third light intensity is recorded in a first range at a discriminating boundary for particles of first and second classifications, second boundary information wherein the third light intensity is recorded in a second range at a discriminating boundary for particles of first and second classifications, and discriminating information wherein identifiers for particles of the first and second classifications are recorded in cells bounded and not bounded by the discriminating boundary, respectively; and a particle identifying portion that evaluates a particle being measured as a particle of the first classification when the identifier for a particle of the first classification is acquired based on the measured values for the first and second light intensities and the measured value for the third light intensity falls between the first and second boundary values.