An impulse line-clogging detecting apparatus. The apparatus is provide with: a differential pressure detecting unit that detects a differential pressure of a fluid, and outputs time-series data of the differential pressure. Fluctuations are determined by a differential pressure fluctuation calculating unit that calculates a differential pressure fluctuation, and a fluctuation variance calculating unit that calculates a variance of the differential pressure fluctuation. Based upon the calculated variance, a variance ratio calculating unit calculates a variance ratio of the differential pressure fluctuation variance to a differential pressure fluctuation variance obtained in advance in a normal state of the high and low pressure side impulse lines. A variance ratio correcting unit calculates a correction value for suppressing a change of the variance ratio. Finally; a clogging determining unit determines whether the high and low pressure side impulse lines are clogged, based on the variance ratio corrected by the variance ratio correcting unit.