(EN) Disclosed herein is an automatic dialing device for telephones, which is used when positioned on or near the body of a telephone. The automatic dialing device includes a manipulation button for allowing a user to manipulate the device, a Dual Tone Multi Frequency (DTMF) storage and output unit for storing telephone number(s) and outputting a stored DTMF signal according to manipulation of the manipulation button, first and second connectors for transmitting the output DTMF signal and connecting with a trunk line and a telephone, respectively, and an interfacing unit for interfacing the DTMF storage and output unit with the trunk line and the telephone so that the DTMF signal is used only while the handset of the telephone is picked up, that is, the hook switch of the telephone is turned off.