The purpose of the present study was to analyze feeding behavior in infants kinesiologically and psychologically. For purposes of analysis, we divided infancy into four stages. (1) 1st stage (0-2 months) : We observed sucking reflex and rooting reflex. We believed that though these are seen to be reflexive behavior, intellectual factors were also involved. (2) 2 nd stage (3-5 months) : We observed the acquired movements of the oral region. We explained kinesiologically that these were inhibitions of oral reflexes by the upper neuron and co-contraction of muscles of the oral region, and psychologically that they were coordination of the schemes. (3) 3 rd stage (6-9 months) : We observed the differentiated movements of the oral region. In particular we discussed the chewing movement and thought it kinesiologically to be a mechanism of reciprocal innervation, and psychologically to be an understanding of quantitive relationship in the secondary scheme. (4) 4 th stage (10-11 months) : We observed the coordinative movements of the oral region. We described kinesiologically that the oral region adapted to characteristics of food by development of equilibrium reaction, visual signals and so on. Psychologically, we believed that the infant's intention as defined by Piaget was acting on food intake via spoon or straw.