This paper proposes a method to suppress the vibrations of a machine-room-less elevator. Up until recently, elevators have needed a machine room. Now a machine can be installed in the hoistway because the Building Standard Acts have been amended. We have developed a machine-room-less elevator which has the machine in the pit of the hoistway. The rope is longer and number of pulleys is greater than in previous elevators. This tends to cause vibration in the cage. This vibration, in turn, deteriorates the ride quality. To suppress vibration, the design parameters must be optimized such that the transfer function between these disturbances and cage acceleration has a minimal value. The masses, spring constants, and damping coefficients are considered as control parameters, and optimized in the best design. The spring constants and damping coefficients of the thimble rods are important to suppress vibration. In experiments we reduced cage vibration to two thirds that in our previous design, and thus, improved the ride quality.