Long mat with hydroponically grown rice seedlings (hereafter referred to as LMHS) with a mat size of 6 m in length and 28 cm in width, was designed to develop a labor-saving rice transplanting system. The rice seedlings were grown in a newly developed nursery device for about 2 weeks and the plant length reached 10 to 15 cm. The seedling mat was composed of entangled plant roots and nonwoven cloth and it was strong enough to be handled. LMHS were transformed into roll type seedlings by rolling up. The weight of a mat with roll type seedlings was about 12 kg and approximately 1/5 of that of a conventional mat with young seedlings raised in a soil bed (hereafter referred to as CMSS). A rice transplanter was designed and tested to transplant the roll type seedlings in paddy fields. The rate of damaged seedlings immediately after transplanting was 30 to 50%. However, the minimum rate of missing hills after rooting was 3%, when the number of plants per hill ranged from 7 to 8. Working rate of the transplanter was approximately 0.5 ha/h for a working speed of 1.13 m/s and a working width of 1.8 m. Rice yield in the case of LMHS was assumed to be equal to that of CMSS.