Provided is an apparatus for adjusting an envelope signal delay in an envelope-tracking power amplifier. The apparatus includes: an envelope signal providing unit configured to provide an envelope signal; a variable negative group delay unit configured to adjust a group delay of the envelope signal received from the envelope signal providing unit and output the adjusted envelope signal; an envelope modulator configured to modulate the envelope signal outputted from the variable negative group delay unit; a group delay difference detecting unit configured to detect a group delay difference between the envelope signal which is outputted from the envelope signal providing unit and the envelope signal which is outputted from the envelope modulator; and a control signal generating unit configured to generate a control signal to control a group delay value of the variable negative group delay unit according to the group delay difference.