In a collision detection device for a vehicle, the bumper absorber includes general parts and holding parts alternately in a lengthwise direction of the groove portion. In each of the general parts, a predetermined clearance is formed between an inner wall surface of the groove portion on at least one side of vehicle up and down sides, and the detection tube member. Each of the holding parts is in contact with a surface of the detection tube member on at least one side of vehicle up and down sides, and vehicle front and rear sides to hold the detection tube member. A holding part ratio, which is a ratio of a part of the detection tube member held by the holding parts to a unit length of the detection tube member, is set to be smaller than a predetermined value.