The utility model discloses a conveying-belt sampling device. The conveying-belt sampling device comprises a semicircular groove rotation mechanism, a transversal blowing mechanism, a transversal-to-vertical rotation mechanism and a rotary tube blowing mechanism, wherein the semicircular groove rotation mechanism is installed above a conveying belt; materials on the conveying belt pass through the space above the semicircular groove rotation mechanism and then are conveyed by the conveying belt; the transversal blowing mechanism is connected with the first end of the semicircular groove rotation mechanism; the second end of the semicircular groove rotation mechanism is used for emitting a sample to the first end of the transversal-to-vertical rotation mechanism; the second end of the transversal-to-vertical rotation mechanism is connected with the rotary tube blowing mechanism. According to the conveying-belt sampling device disclosed by the utility model, the product is transmitted from the semicircular groove rotation mechanism, after the sample is taken by the semicircular groove rotation mechanism, the sample is converted to a vertical state from a horizontal state by the transversal-to-vertical rotation mechanism to be emitted, thus avoiding extremely high space occupation brought by directly bending a pipeline; a first embedded thin tube for sampling is embedded in a semicircular groove, thus omitting an external pipeline.