An electronic device comprising: a radiating portion configured to radiate a signal at a specified frequency; a feeding portion electrically connected with the radiating portion; a tunable element electrically connected with one point of the radiating portion and configured to influence an electrical length of the radiating portion; and a control circuit electrically connected with the radiating portion, the feeding portion, and the tunable element, wherein the control circuit is configured to: transmit a signal at the specified frequency to the radiating portion through the feeding portion; acquire values associated with reflection of the signal corresponding to a time constant of the tunable element and a plurality of time constants adjacent to the time constant of the tunable element when transmitting the signal; and control the tunable element to have a time constant corresponding to a smallest value among the values associated with the reflection; characterised in that the control circuit is further configured to: acquire the values associated with the reflection, if at least one of strength of the signal, strength of a signal reflected from the radiating portion when the signal is radiated by the radiating portion, a reflection coefficient associated with the signal and the reflected signal, and a VSWR associated with the signal and the reflected signal is changed in excess of a specified range. a radiating portion configured to radiate a signal at a specified frequency; a feeding portion electrically connected with the radiating portion; a tunable element electrically connected with one point of the radiating portion and configured to influence an electrical length of the radiating portion; and a control circuit electrically connected with the radiating portion, the feeding portion, and the tunable element, wherein the control circuit is configured to: transmit a signal at the specified frequency to the radiating portion through the feeding portion; acquire values associated with reflection of the signal corresponding to a time constant of the tunable element and a plurality of time constants adjacent to the time constant of the tunable element when transmitting the signal; and control the tunable element to have a time constant corresponding to a smallest value among the values associated with the reflection; transmit a signal at the specified frequency to the radiating portion through the feeding portion; acquire values associated with reflection of the signal corresponding to a time constant of the tunable element and a plurality of time constants adjacent to the time constant of the tunable element when transmitting the signal; and control the tunable element to have a time constant corresponding to a smallest value among the values associated with the reflection; characterised in that the control circuit is further configured to: acquire the values associated with the reflection, if at least one of strength of the signal, strength of a signal reflected from the radiating portion when the signal is radiated by the radiating portion, a reflection coefficient associated with the signal and the reflected signal, and a VSWR associated with the signal and the reflected signal is changed in excess of a specified range.