The possibility was examined that grammatical structure was acquired by “contextual generalization” Experiment 1 was the Verbal Group using sentences accompanied with particles “i”,“ga”,“to.” Experiment 2 was the Verbal Group using sentences not accompanied with particles. Experiment 3 was the Non-Verbal Gtoup. Each Experimental Group had eight subgroups: 2 (normal order sentence vs. reversed order sentence)×2 (two words sentence vs. four words sentence)×2 (five year old infants vs. four year old infants). Ss were 288 kindergarten infants. Half of them were five years old, and the others were four years old. They were divided into 24 subgroups. They were required to arrange picture cards. Results: (1) The Verbal Group was better than the Non- Verbal Group. (2) The Verbal Group using sentences accompanied with particles was better than the Verbal Group using sentences not accompanied with particles. (3) Five year old infants could do reversed order sentence as well as normal order sentence. But four year old infants could not do so. (4) Two words sentence was easier than four words sentence. (5) Five year old infants were better than four year old infants.