Abstract: An apparatus for automatically measuring dust concentration in flue gas includes (a) a sampling unit for sampling dust in flue gas; (b) a measuring unit for measuring a gas flow of the flue gas; and (c) a feeding and weighing unit for feeding and weighing a filter paper for filtering the sampled gas, the feeding and weighing unit including (i) a filter paper cassette for storing the filter paper, (ii) a filter paper stocker for storing a plurality of the filter paper cassettes, (iii) a cassette pusher unit for pushing a filter paper cassette out of the filter paper stocker, (iv) a filter paper ascending unit for raising the filter paper, (v) a filter paper drier for drying the filter paper, (vi) a filter paper transfer arm for transferring the filter paper between the filter paper cassette, the filter paper ascending unit and the filter paper drier, (vii) a vibration-free balance for balancing the filter paper, and (viii) a hot air generation unit.