A boundary acoustic wave device in which a first medium to a fourth medium are laminated and an electrode is disposed between a first medium and a second medium is provided, wherein the boundary acoustic wave device has a small absolute value of temperature coefficient of delay time and good temperature characteristics. A boundary acoustic wave device (1) in which a first medium (11) to fourth medium (14) are laminated in that order and, an electrode including an IDT electrode (16) is disposed at an interface between the first medium (11) and the second medium (12), and in a structure formed by laminating the fourth medium (14)/the second medium (12)/the electrode/the first medium (11), the temperature coefficient of delay time TCD of a boundary acoustic wave takes on a positive value, the fourth medium or the second medium has a positive temperature coefficient of sound velocity TCV, the first medium (11) has a negative temperature coefficient of sound velocity TCV, and the sound velocity of transverse wave of the third medium (13) is specified to be smaller than the sound velocity of transverse wave of the fourth medium (14) and/or the second medium (12).