A collision determining apparatus for a vehicle includes: a first acceleration measuring device; a second acceleration measuring device; a movement amount calculating device; a change in movement speed calculating device; a first collision determining threshold value setting device which sets a collision determining threshold value for a correlation between the amount of movement of the occupant and the change in movement speed of the occupant based on the acceleration which is measured by the first acceleration measuring device; a first collision determining device which determines whether or not the correlation exceeds the collision determining threshold value; and a control signal generating device which generates a control signal which controls operations of an occupant protection apparatus, in accordance with a result of a determination by the first collision determining device.