PURPOSE: To enable producing a plurality of car shapes and car types with high accuracy in the same line in such a way that retaining members and jig members which are changed over by signals from car type detecting means are provided on apparatuses and devices for carrying in, positioning, assembling and welding of all the parts in the car body assembling line.

CONSTITUTION: When a B car type floor is carried in during assembly of A car type, respective change-over is done for retaining members 430, 431 of means 411 for the purpose that signals from a car type detecting means in the front or from a computer in the central control room give influence to interchange fixtures of side body assembling mechanism 10 from A car type purpose to B car type purpose, and to carrying rear upper panels in place, retaining members 393, 394 for rear waist carrying in means 371, retaining members 350, 351 for cowl assembly carring in means 331, arms 168, 169 for receiving posts 161, and receiving seats 299, 300 for side body receivers 292. Besides, during assembly of A or B type assembly, in case where there are car type changes from sedan series to hard top series, all what has to be done is to interchange jig members of side body assembling mechanisms 10.