PURPOSE: To provide the title thin type transformer having excellent assembling capacity capable of miniaturizing and settling the problem of clearance when a core and a terminal base are separated as well as avoiding the coil disconnection.

CONSTITUTION: Within a terminal base 1 tieing up a lead wire of a coil, a ferrite made lower side core half body 2 and a resin made terminal part 3 implanted with the terminals 4 are previously formed integrally with each other while a flat coil 5 is fixed on the core half body 2 on the lower side of this terminal base 1 so as to be covered with an upper side core half body 2'.