Suspension device for vehicle

A suspension device for a vehicle, comprising first and second suspensions for respectively suspending, from a vehicle body, first and second wheels arranged separately from each other in a vehicle longitudinal direction, wherein:

• a first product is set as a product ((Xs2/F1)·(F1/F)) of a first transmission force characteristic (Xs2/F1) (s is Laplacian) represented by a first transmission force (F1), which is a force received by the vehicle body from the first wheel, and a displacement (X) of the vehicle body in the longitudinal direction when a first longitudinal force (F) is input to the first wheel and a sensitivity (F1/F) of the vehicle, which is a ratio of the first transmission force (F1) to the first longitudinal force (F);
• a target complex spring constant is set as a complex spring constant in the vehicle longitudinal direction of the second suspension in a case where an evaluation indication value correlating with a square ({(Xs2/F1)·(F1/F)}2) of the first product takes a minimum value out of values that are likely to be taken by the evaluation indication value in a predetermined frequency range (fl to fh) set in advance so as to include a peak frequency (fs) corresponding to a peak value of the first transmission force characteristic;
• and
• the complex spring constant in the vehicle longitudinal direction of the second suspension is set to the target complex spring constant.