The invention discloses a revolving double-crank transplanting mechanism of a seedling planting machine. A planet carrier rotates around the center of fixed cylindrical gears; a transplanting mechanism consisting of two double-crank mechanisms are mounted on the two ends of the planet carrier; the frame of the double-crank mechanisms is the planet carrier; the cranks of the double-crank mechanisms are driven to rotate by two cylindrical gears; the mechanism which is composed of the cylindrical gears and a plurality of member bars has no non-circular gears, thus realizing two seeding actions for one rotation around the planet carrier, and the track of seedlings meets the requirements of agricultural technology.