A vehicle lighting source adapter includes a holder, terminals, and cables connected to the terminals. The holder has its front end disposed with an insertion plate. The insertion plate includes an upper surface and a lower surface. Each of the upper and lower surfaces is disposed with connection channels and insertion blocks. Each connection channel includes a first fillister and a second fillister. A retainer is disposed to each fillister. Each terminal is inserted into and partially exposed form the first fillister and has its snap portion to be restricted by the retainer.