A touch sensing system comprises a touchscreen with a plurality of touch electrodes, to which a touchscreen driving signal is applied, and a stylus pen that generates a pen driving signal based on the touchscreen driving signal and sends the same to the touchscreen. The stylus pen comprises: an amplifier that amplifies the touchscreen driving signal to generate an amplified signal; a comparator that compares the amplified signal with a preset reference voltage to generate a comparator output signal; and a signal processor that measures the pulse width of the comparator output signal, adjusts an amount of delay based on a measurement, and determines an output timing of the pen driving signal based on an adjusted amount of delay to synchronize the pen driving signal with the touchscreen driving signal.