In a drive assist device, a first condition that an inter-vehicle distance between a preceding vehicle and an own vehicle is smaller than a first threshold, a second condition that a speed of the preceding vehicle relative to the own vehicle is lower than a second threshold, a third condition that a speed of an adjacent vehicle that travels on an adjacent lane to the own vehicle is lower than a third threshold, and a fourth condition that an acceleration rate of the adjacent vehicle is lower than a fourth threshold are defined. When at least one of the first condition and the second condition and at least one of the third condition and the fourth condition are satisfied, the drive assist ECU executes acceleration restraint control of a driving device and/or a braking device such that an acceleration rate of the own vehicle is “0” or lower.