The invention discloses a wide/narrow row potted-seedling transplanting mechanism with bevel gear and noncircular bevel gear crossed-axis planetary gear trains. A seedling needle of the existing wide/narrow row rice potted-seedling transplanting mechanism is large in lateral offset, inaccurate in seedling taking position and very low in seedling taking rate during seedling taking. According to the wide/narrow row potted-seedling transplanting mechanism, two planetary gear trains are symmetrically arranged at two ends of a central shaft and are driven by four-stage gear pairs, wherein the first-stage gear pair is a crossed-axis cylindrical bevel gear pair, and the second-stage, third-stage and fourth-stage gear pairs are noncircular bevel gear pairs. By using the planetary gear trains, a rice transplanting point can laterally offset relative to a seedling taking point after a seedling is taken by a seedling taking claw, so that the wide/narrow row potted-seedling planting is realized, and the seedling taking claw can favorably form an 8-shaped spatial motion track; and compared with two-stage gear transmission, the four-stage gear transmission has the advantages that the minimum lateral offset of the track during seedling taking can be up to 1.8mm, and the seedling taking claw is in a straight seedling taking posture, so that the seedling taking success rate is ensured. Meanwhile, the four-stage transmission can keep transmission ratio curves of all levels of gears more flat and is beneficial to generation of the noncircular bevel gears meeting the requirements of convexity and pressure angles.