A leaf spring device (1, 1A, 1B, 1C) comprising a plurality of leaf springs (11, 12) provided to be stacked in a vertical direction, wherein a restricting protrusion (14,114,214) is provided on a surface of one of two leaf springs (11,12) adjacent to each other in the vertical direction, a recessed part (13,213) is formed on a surface of the other thereof, and the restricting protrusion (14,114,214) is inserted into the recessed part (13,213), a longitudinal direction of each of the restricting protrusion (14,114,214) and the recessed part (13,213) coincides with a longitudinal direction of the leaf springs (11,12) when viewed from the vertical direction, central portions of the leaf springs, (11,12) the restricting protrusion (14,214), and the recessed part (13,213) coincide with each other when viewed from the vertical direction, the restricting protrusion (14,114,214) includes a first side surface (21,121,221) and a second side surface facing a plate width direction perpendicular to the vertical direction and the longitudinal direction, extending in the longitudinal direction, and positioned on both sides sandwiching the central portions of the leaf springs (11,12), the restricting protrusion (14,214), and the recessed part (13,213) in the plate width direction when viewed from the vertical direction, the recessed part (13,213) includes a third side surface (23,223) and a fourth side surface (24,224) facing the plate width direction, extending in the longitudinal direction, and facing each other with the restricting protrusion sandwiched therebetween in the plate width direction, the first side surface and the third side surface face each other in the plate width direction, the second side surface and the fourth side surface face each other in the plate width direction, characterised in that, a first inclined surface is formed on one side surface of the first side surface and the third side surface to become further away from the other side surface thereof in the plate width direction from the central portion toward a first direction in the longitudinal direction, and a second inclined surface (17,217) is formed on one side surface of the second side surface (22,122,222) and the fourth side surface (24,224) to become further away from the other side surface thereof in the plate width direction from the central portion toward a second direction opposite to the first direction in the longitudinal direction. a restricting protrusion (14,114,214) is provided on a surface of one of two leaf springs (11,12) adjacent to each other in the vertical direction, a recessed part (13,213) is formed on a surface of the other thereof, and the restricting protrusion (14,114,214) is inserted into the recessed part (13,213), a longitudinal direction of each of the restricting protrusion (14,114,214) and the recessed part (13,213) coincides with a longitudinal direction of the leaf springs (11,12) when viewed from the vertical direction, central portions of the leaf springs, (11,12) the restricting protrusion (14,214), and the recessed part (13,213) coincide with each other when viewed from the vertical direction, the restricting protrusion (14,114,214) includes a first side surface (21,121,221) and a second side surface facing a plate width direction perpendicular to the vertical direction and the longitudinal direction, extending in the longitudinal direction, and positioned on both sides sandwiching the central portions of the leaf springs (11,12), the restricting protrusion (14,214), and the recessed part (13,213) in the plate width direction when viewed from the vertical direction, the recessed part (13,213) includes a third side surface (23,223) and a fourth side surface (24,224) facing the plate width direction, extending in the longitudinal direction, and facing each other with the restricting protrusion sandwiched therebetween in the plate width direction, the first side surface and the third side surface face each other in the plate width direction, the second side surface and the fourth side surface face each other in the plate width direction, characterised in that, a first inclined surface is formed on one side surface of the first side surface and the third side surface to become further away from the other side surface thereof in the plate width direction from the central portion toward a first direction in the longitudinal direction, and a second inclined surface (17,217) is formed on one side surface of the second side surface (22,122,222) and the fourth side surface (24,224) to become further away from the other side surface thereof in the plate width direction from the central portion toward a second direction opposite to the first direction in the longitudinal direction.