An elastic wave device comprising a piezoelectric layer and configured to propagate A 1, S 0, or SH 0 mode plate waves, the A 1 plate waves being anti-symmetric mode Lamb waves having one node in the thickness direction of the piezoelectric layer, the S 0 mode plate waves being symmetric mode Lamb waves having no node in the thickness direction of the piezoelectric layer, and the SH 0 mode waves being shear horizontal waves having no node in the thickness direction of the piezoelectric layer, the elastic wave device comprising: a supporting substrate; an acoustic reflection layer on the supporting substrate; a piezoelectric layer made of LiNbO 3 or LiTaO 3 on the acoustic reflection layer; and an IDT electrode on an upper or lower surface of the piezoelectric layer, the piezoelectric layer being thinner than a period of fingers of the IDT electrode, wherein: the acoustic reflection layer has a low-acoustic-impedance layer and a high-acoustic-impedance layer having a higher acoustic impedance than an acoustic impedance of the low-acoustic-impedance layer; characterised in that the low-acoustic-impedance layer is made of SiO 2, and the high-acoustic impedance layer is made of at least one material selected from the group consisting of W, LiTaO 3, Al 2 O 3, AlN, LiNbO 3, SiN, and ZnO.; and the Euler Angles of the LiNbO 3 or LiTaO 3 of the piezoelectric layer fall within a range specified in Table 1 [Table 1] Piezoelectric material LiNbO 3 LiTaO 3 Mode A 1 (0, 20, 0) to (0, 50, 0) (0, 12, 0) to (0, 48, 0) S 0 (90, 90, 25) to (90, 90, 44) (90, 90, 13) to (90, 90, 36) SH 0 (0, 95, 0) to (0, 132, 0) (0, 100, 0) to (0, 134, 0) a supporting substrate; an acoustic reflection layer on the supporting substrate; a piezoelectric layer made of LiNbO 3 or LiTaO 3 on the acoustic reflection layer; and an IDT electrode on an upper or lower surface of the piezoelectric layer, the piezoelectric layer being thinner than a period of fingers of the IDT electrode, wherein: the acoustic reflection layer has a low-acoustic-impedance layer and a high-acoustic-impedance layer having a higher acoustic impedance than an acoustic impedance of the low-acoustic-impedance layer; characterised in that the low-acoustic-impedance layer is made of SiO 2, and the high-acoustic impedance layer is made of at least one material selected from the group consisting of W, LiTaO 3, Al 2 O 3, AlN, LiNbO 3, SiN, and ZnO.; and the Euler Angles of the LiNbO 3 or LiTaO 3 of the piezoelectric layer fall within a range specified in Table 1 [Table 1] Piezoelectric material LiNbO 3 LiTaO 3 Mode A 1 (0, 20, 0) to (0, 50, 0) (0, 12, 0) to (0, 48, 0) S 0 (90, 90, 25) to (90, 90, 44) (90, 90, 13) to (90, 90, 36) SH 0 (0, 95, 0) to (0, 132, 0) (0, 100, 0) to (0, 134, 0) the acoustic reflection layer has a low-acoustic-impedance layer and a high-acoustic-impedance layer having a higher acoustic impedance than an acoustic impedance of the low-acoustic-impedance layer; characterised in that the low-acoustic-impedance layer is made of SiO 2, and the high-acoustic impedance layer is made of at least one material selected from the group consisting of W, LiTaO 3, Al 2 O 3, AlN, LiNbO 3, SiN, and ZnO.; and the Euler Angles of the LiNbO 3 or LiTaO 3 of the piezoelectric layer fall within a range specified in Table 1 [Table 1] Piezoelectric material LiNbO 3 LiTaO 3 Mode A 1 (0, 20, 0) to (0, 50, 0) (0, 12, 0) to (0, 48, 0) S 0 (90, 90, 25) to (90, 90, 44) (90, 90, 13) to (90, 90, 36) SH 0 (0, 95, 0) to (0, 132, 0) (0, 100, 0) to (0, 134, 0)