To change spring characteristics to a non-linear form according to the weight of a vehicle by using a simple mechanism.

The vehicular suspension device is structured of a leaf spring 12, to which an axle housing 20 is fixed in an intermediate part, a spring bracket 14 for fixing one end of the leaf spring 12 to a car body frame 10 freely to swing, a shackle 16 and a spring bracket 18 for fixing the other end of the leaf spring 12 to the car body frame 10 freely to swing, an air cylinder 22 for increasing and reducing volume of an inner space thereof according to reciprocating operation of the movable part 22B with abutment of a tip of the movable part 22B on the top surface of the leaf spring 12 when a bending degree of the leaf spring 12 is a predetermined value or more, and an air reservoir 26 for communicating the air cylinder 22 with the inner space. Spring characteristic is changed to a non-linear form according to the weight of a vehicle by making the air cylinder 22 function as an air spring.