Word order constitutes a fundamental cue for sentence comprehension. Previous research on English and French found evidence for adult-like word order knowledge in 19-month-olds, but little is known about early word order development in languages with frequent word order alteration and argument omissions that reduce positive evidence for the canonical word order. To address this question, we conducted (i) a distributional analysis of word order variation in child-directed Japanese, and (ii) a preferential-looking study with Japanese 19- and 30-month-olds, using the same design as a previous study on French 19-month-olds. Our analysis of 17726 child-directed utterances revealed that 91% of the input was uninformative for identifying the canonical SOV order. Next, our preferential-looking experiment revealed that Japanese 19-month-olds fail to understand sentences with a canonical word order, unlike French 19-month-olds or Japanese 30-month-olds. We suggest that the sparseness of SOV in the input delays the development of word order knowledge.