A mobile radio communication device has an antenna, a circuit board to which the antenna is connected and on which a plurality of electronic elements are mounted, an inner casing formed of resin and housing the circuit board, and an outer casing of resin covering the inner casing. The antenna is located on that portion on an outer face of the inner casing which is covered by the outer casing, and the antenna is disposed to penetrate into the inside of the inner casing through a hole formed on the inner casing, and the feeding end of the antenna is connected to the circuit board. This allows the antenna to be spaced apart from other electronic elements on the circuit board in the lower body without protruding the antenna outside, to achieve a sufficient antenna property by elimination of effects from other electronic elements.