Large numbers of crab shells are disposed of as food waste in the food processing process. Chitin nanofiber (CNF) refers to chitin extracted from crab shells in the form of ultrafine fibers that enable uniform dispersion in water. We explored the feasibility of using CNF materials as plant growth promoters. We investigated the effects of CNF application with fertilizer and its various application methods on the growth of the komatsuna plant cultivated in Entisols and Andosols with the application of CNF materials. The surface application of CNF materials had plant growth-promoting effects in both Entisols and Andosols. The topdressing treatment was more effective in promoting plant growth in Entisols. The inorganic nitrogen content absorbed by plants in the topdressing treatment was lower than that in the basal application treatments because the CNF added during the latter half of the cultivation period was not fully decomposed before the completion of cultivation. The calcium content of plants in the basal application treatment of CNF/protein/calcium carbonate was higher than that in the topdressing treatments, indicating that the calcium encasing the CNF was absorbed by the plants. The cultivation of plants with the application of CNF materials promoted nitrogen utilization efficiency and plant growth.