A device and a method for preventing driving under influence, may include a first measuring device configured for detecting alcohol in indoor air of a vehicle, and a processor connected to the first measuring device, wherein the processor performs a first check of checking a presence or an absence of the alcohol in the indoor air through the first measuring device before a driver boards the vehicle, performs a second check of checking the presence or the absence of the alcohol in the indoor air through the first measuring device after the driver boards the vehicle, and determines whether there is a possibility that the driver is drunken based on the results of performing the first check and the second check.