A portable information terminal device has a plurality of casings providing a
front
surface and a rear surface, respectively. The casings have walls defining spaces
in which speakers are housed and thicker than walls thereof that define a space
in which a component including an internal circuit is housed. The walls defining
the spaces in which speakers are housed are prevented from causing resonance due
to vibrations of the speakers. The walls that define the space in which the component
including the internal circuit is housed may be of a minimum thickness required
irrespective of resonance caused by vibrations of the speakers. With the above
arrangement, the portable information terminal device is small in size and weight.