The invention relates to the technical field of agricultural machinery, in particular to an automatic whole-row grafting device for grafted seedlings. The device comprises a rack (1), an electric control cabinet (3), a scion conveying mechanism I (5), a scion conveying mechanism II (8), a grafted seedling conveying mechanism (6), a scion clamping mechanism (87), a rootstock clamping mechanism (88), a scion seedling cutting mechanism (17), a rootstock seedling cutting mechanism (11), a scion seedling gathering mechanism (2), a rootstock seedling gathering mechanism (12) and an automatic whole-row grafting clamp conveying mechanism (89). According to the automatic whole-row grafting device for the grafted seedlings, plug seedling supply, whole-row seedling grabbing, seedling cutting, fixing and grafting of plug rootstock seedlings and plug scion seedlings are realized, and the whole operation process is automatically completed by a machine; the plug seedlings are rapidly grafted, the labor efficiency of grafting operation is improved, and the labor force is saved.