A transformer having a reduced inner space, so as to reduce the amount of insulation seal material injected, a set substrate−dedicated area, size, and cost of the transformer. A low−voltage coil, a high−voltage coil, and a focus pack (3) are built in an external case (2) and a pair of U−shaped cores (1) is inserted in the vertical direction into the coil center portion, so as to constitute a closed magnetic circuit. A leg portion (1a) of the core (1) is arranged with an angle &thetas; in the direction apart from the adjacent surface of the external case (2) with respect to the reference axis X which is a center line of a U−shaped open portion of U−shaped terminals (6a to 6j) for the low−voltage coil.
