We describe vitamin D deficiency rickets in an infant nursed with soybean milk (not specifically designed for infants) instead of cow's milk-based infant formula. Symptoms included irritability and carpopedal spasm when crying. The infant's condition improved with nutrition by vitamin-enriched cow's milk-based infant formula, oral administration 1 alpha-hydroxy vitamin D3 and exposure to sunlight. Content analysis of the milk showed very low calcium, phosphate, magnesium and vitamin D levels compared to cow's milk-based infant milk formulas. This case highlights the unsuitability of soybean milk as the sole provider of infant nutrition and demonstrates the false perception that soybean milk is a healthy food for infants. It is necessary to be cautious about not only health claims for soybean milk, but also today's health and natural food booms. Social enlightenment and correction of such misperceptions are necessary.