The characteristics of the spoken language used to address infants have been eagerly studied as a part of the language acquisition research. Because of the uncontrollability factor with regard to the infants, the features and roles of infantdirected speech were tried to be revealed by the comparison of speech directed toward infants and that toward other listeners. However, they share few characteristics with infants, while infants have many characteristics which may derive the features of IDS. In this study, to solve this problem, we will introduce a new approach that replaces the infant with an infant-like robot which is designed to control its motions and to imitate its appearance very similar to a real infant. We have now recorded both infant-and infantlike robot-directed speech and are constructing both corpora. Analysis of these corpora is expected to contribute to the studies of infant-directed speech. In this paper, we discuss the contents of this approach and the outline of the corpora.