In an air intake device for motorcycle, an air cleaner (36) having an front end formed with a main intake port (41) is disposed between a pair of left and right main frame pieces (1a, 1b) forming a main frame (1). An introducing passage (43) is formed within the main frame (1) for capturing an incoming wind. An intake air introducing port (40) of the introducing passage (43) is provided at a location rearwardly of the main intake port (41) in the main frame piece (1a, 1b). An intake air discharge port (39) is defined in an intermediate portion of a front portion of the main frame (1) with respect to a motorcycle widthwise direction so as to open rearwardly and to be fluid connected with the main intake port (41). A sub intake port (42) is provided in communication with the main intake port (41) so as to introduce an intake air (A) into the main intake port (41).