A collision detecting apparatus for a vehicle includes a bumper acceleration sensor, a floor acceleration sensor, a pressure sensor, and a processor including a vehicle collision determining unit and a threshold variably controlling unit. The vehicle collision determining unit is configured to determine a state of collision of the vehicle by comparing a detection value of the pressure sensor with a first threshold, and comparing a detection value of the bumper acceleration sensor with a second threshold when the detection value of the pressure sensor is greater than the first threshold. The threshold variably controlling unit is configured to change a threshold of the floor acceleration sensor from a third threshold to a fourth threshold in a case where: the detection value of the pressure sensor is greater than the first threshold; and the detection value of the bumper acceleration sensor is equal to or less than the second threshold.