Provided is a signal generation device used for an information input system using an ultrasonic signal. A portion of a pen core portion is designed to have a different cross-sectional area (diameter) so that the portion having a different cross-sectional area is held by an inner portion of a housing or a cap member. Therefore, the pen core portion can be naturally supported without use of an additional configuration such as a retainer. Particularly, in a signal generation device in the related art, if elasticity of a retainer is weakened due to long term use, the pen core cannot be supported. However, according to the present invention, since the pen core is supported by using a structural inner portion in the housing, the pen core can be stably supported irrespective of long term use.