PURPOSE: To effectively reduce generation of vibration at both ends of a crank shaft by providing a coupling member for intercoupling bearing caps and a damper mounted on either one end or the other end of the crank shaft.

CONSTITUTION: Since vibration reducing structure of an engine comprises a coupling member 34 and a damper 38, only first and fifth bearing caps 26a and 26e positioned at both ends of a crank shaft 22 are intercoupled through the coupling member 34. Bending vibration of the crank pulley 30 side of the crank shaft 22 and that of the fly wheel 32 side are coupled together. The coupled bending vibrations are both damped by means of a damper 38 mounted on the crank pulley 30. Meanwhile, by intercoupling the bearing caps 26a and 26e in a manner described above, mounting rigidity of the bearing caps 26a and 26e themselves is increased, the bearing caps are suppressed from being opened with respect to a rotary axis, and vibration is effectively suppressed.