A rice seedling transplanting machine comprising prepared gripper arms capable of switching an expanding form and a stacking form without manual operation, and inhibiting an expanding and supporting mechanism from rotating when the machine body shakes in the concave-convex land. The prepared gripper arms (5) are arranged on the side of a travelling vehicle body; the expanding and supporting mechanism (1) for supporting carrying tables of the prepared gripper arms to move is arranged on the prepared gripper arms; an actuator (14a) is arranged on the rice seedling transplanting machine; the actuator enables the expanding and supporting mechanism to act to switch the stacking form of the carrying tables of the prepared gripper arms arranged along the vertical direction and the expanding form of the carrying tables of the prepared gripper arms arranged along the horizontal direction; a force applying device (15) for applying force to the expanding and supporting mechanism is arranged on the prepared gripper arms respectively; the force applying device is used for applying force to the expanding force side of the expanding and supporting mechanism at the beginning of movement when the prepared gripper arms switch to the expanding force from the stacking form, and applying force to the stacking force side of the expanding and supporting mechanism at the end of movement.