231 and the third folding element 233 are aligned axially on the other hand the front frame 211 is separated from the rear frame 221 so as to fold up the folding bicycle and therefore the folding mechanism 23 is partially exposed from at least one of the front frame 211 and the rear frame 221 thereby allowing the front wheel 212 and the rear wheel 222 to be parallel by positioning the first folding element 231 and the third folding element 233 in parallel the fold securing mechanism not shown secures in position the front body 21 and the rear body 22 while the front wheel 212 and the rear wheel 222 are parallel the fold securing mechanism is preferably an s shaped hook detailed description of the fold securing mechanism is omitted herein as the production of s shaped hooks is a mature and well known technology referring to fig4 a the first folding element 231 is fixedly inserted into the front frame 211 leaving one end of the first folding element 231 exposed from the front frame 211 the exposed end of the first folding element 231 has a first pivot portion 2311 in other words the first pivot portion 2311 is exposed from the front frame 211 the second folding element 232 has a second pivot portion 2322 corresponding in position and shape to the first pivot portion 2311 and a third pivot portion 2323 the first pivot portion 2311 is pivotally coupled to and freely rotatable about the second pivot portion 2322 of the second folding element 232 the third folding element 233 has a fourth pivot portion 2334 corresponding.