To provide an operation assisting device for a vehicle capable of interrupting traveling control at suitable timing when capturing of a preceding vehicle gets unstable.

When capturing and losing of the preceding vehicle by IPU5 is frequently repeated, PCU6 adds a counter value to a determination counter Ct2 by action of a lost counter Ct1. When the preceding vehicle is continuously captured or when the preceding vehicle is continuously lost, the counter value is periodically subtracted from the determination counter Ct2 by action of a clear counter Ct0. Thereby, the determination counter Ct2 can be suitably increased/decreased according to the capturing state of the preceding vehicle, and interruption of traveling control at the suitable timing is possible by determining HALT of the traveling control during a time when the determination counter Ct2 becomes at least a second threshold value or less after it arrives at a first threshold value.