A cab rear mounting device includes: a pair of posts disposed at a predetermined interval in a width direction of a vehicle, and fixedly mounted to a vehicle body; strikers mounted to the pair of posts, respectively; a pair of locking devices mounted to the cab, and coupled to each striker to be locked, so as to fix the cab to the vehicle body, or separated from each striker to be unlocked, so as to release the cab from the vehicle body; and damper devices mounted to the posts, respectively, and configured to absorb vibration or shock, thereby promoting a decrease in the number of components, and weight and cost of the vehicle.