In this experiment, I Would observe how preschool children will give a solution when they are given subjects in which they have interest. After that, I would characterize logical constructs of thinking in pre-school children. As a different view point from general researches on logical thinking, I would observe how pre-school children really think logically before they consciously operate and adjust already existing systems and axioms of logic. Experiments Subjects: 60 children in kindegrarten (six years old). Materials: 16 colored pictures of animals on white cards (4cm-4cm). These animals are as follows, fishes: a goldfish, ared tai and a loach. birds: a japanese crane, a sparrow, an owl, a duck and a cock. insects: a butterfly, a cicada and a dragonfly. beasts: a monkey, a goat, a rat, a rabbit and a dog. Picture-book is “a living thing” A book of science (2) by Kazuo Mafune. Doshinsha (in Japanese) 1968. This book shows (1) how animals move, and (2) names of parts in animals. For instance, p.2 pictures of a lion, a cat and a dog.“Beasts walk by legs” p.10 picture of a cow.“A beast has a head, a trunk and 4 legs. The body is covered with hairs” Experiment I A . Teaching group. Subjects 30. First, subjects are taught on distinctive features among “fish”,“bird”,“insect” and “beast” in picture- book. First trial subjects must name 16 animals on cards. If they make mistakes, experimenter teaches them correct names. After that subjects classify 16 cards as they consider them to belong to one group or another. When subjects finished classifications, experimenter asked reasons why they classified as they did. For subjects who classified correctly, experiment is stopped. Other subjects must advance to another trial. Second trial: experimenter instructs subjects to classify these 16 cards into “fishes”,“birds”,“insects”, and “beasts”. When they finished, experimenter asked reasons why they classified as they did. Experiment II B . Non-teaching group. Subjects 30. Experimenter gave subjects no instructions on these animals. First and second trials are as in first experiment. Results (1) Correct classification on scientific thinking was greater in A group than in B. Though subjects of B group classified correctly, their reasons are based on experience. (2) I would set up some stages of logical thinking which appeared in this experiment.(Table 1)