Kunio Maekawa (1905-1986) played an important part in the creation of modern architecture in Japan. The purpose of this study is to clarify the spatial composition of lobby spaces in the Museums designed by him. This study focuses nine works published in Shin-Kenchiku and Kenchiku-Bunka, and analyzes on following three points, Shape of the Plan, Changes of the Section and Position of the Main Opening. As a result, nine lobby spaces can be classified four types: 1) one floor of L shape with a terrace, 2) one floor of straight line with a void, 3) complex of two floors with a void, 4) complex of two floors with a terrace and a void.