The invention discloses a grain sampling device for a grain depot, and relates to the technical field of grain sampling machinery. The grain sampling device comprises a base box; four groups of firstelectric telescopic rods perpendicular to the lower bottom surface are fixedly arranged at the four corners of the lower bottom surface of the base box; horizontal base plates are hinged to the lowerends of the first electric telescopic rods; a controller, a level sensor and a storage battery pack are arranged in the base box; baffle plates are arranged on the two sides of the upper surface of the base box; sampling rods are located at the position, between the baffle plates on the two sides, of the upper surface of the base box; stand columns perpendicular to the upper surface are arranged at the front end of the base box; an inserting rod device is arranged at the upper ends of the stand columns, a rod taking device is arranged at the position, on one sides of the stand columns, of theupper surface of the base box; and the upper end of the inserting rod device is connected with a grain sucking device through a hose. The grain sampling device has the advantages that balance self-adjusting can be realized, inclination can be avoided when the sampling rods are inserted, and the grain depot with a relatively high storage capacity can be sampled under the condition that the remaining space between the grain surface and the depot top is small.