An apparatus for activating a pedestrian detection and collision mitigation system (PDCMS) function of a vehicle, the apparatus comprising: a front detection sensor configured to detect a presence of a pedestrian on a driving lane of the vehicle and a distance and a relative speed between the pedestrian and the vehicle; a vehicle sensor configured to detect a speed of the vehicle; an electronic control unit configured to activate the PDCMS function based on information detected by the front detection sensor and the vehicle sensor; and a warning unit configured to operate so as to inform a driver of a risk of a collision of the pedestrian with the vehicle, wherein the front detection sensor includes: a radar sensor configured to detect the pedestrian on the driving lane of the vehicle using a radio wave reflected from the pedestrian to generate radar detection information; a far-infrared camera sensor configured to imagine heat radiated from the pedestrian to generate far-infrared recognition information; and an information integration processor configured to integrate the radar detection information and the far-infrared recognition information, wherein the PDCMS function includes a collision warning and an activation of an automatic operation of an emergency brake, wherein the electronic control unit is further configured to activate the operation of the PDCMS function, if an initial speed of the pedestrian at a boundary of a driving lane on which the pedestrian is moving is within a first speed range and an initial speed of the vehicle is within a second speed range, the first speed range and the second speed range defining an area in which the PDCMS function is essentially operated. a front detection sensor configured to detect a presence of a pedestrian on a driving lane of the vehicle and a distance and a relative speed between the pedestrian and the vehicle; a vehicle sensor configured to detect a speed of the vehicle; an electronic control unit configured to activate the PDCMS function based on information detected by the front detection sensor and the vehicle sensor; and a warning unit configured to operate so as to inform a driver of a risk of a collision of the pedestrian with the vehicle, wherein the front detection sensor includes: a radar sensor configured to detect the pedestrian on the driving lane of the vehicle using a radio wave reflected from the pedestrian to generate radar detection information; a far-infrared camera sensor configured to imagine heat radiated from the pedestrian to generate far-infrared recognition information; and an information integration processor configured to integrate the radar detection information and the far-infrared recognition information, wherein the PDCMS function includes a collision warning and an activation of an automatic operation of an emergency brake, wherein the electronic control unit is further configured to activate the operation of the PDCMS function, if an initial speed of the pedestrian at a boundary of a driving lane on which the pedestrian is moving is within a first speed range and an initial speed of the vehicle is within a second speed range, the first speed range and the second speed range defining an area in which the PDCMS function is essentially operated. a radar sensor configured to detect the pedestrian on the driving lane of the vehicle using a radio wave reflected from the pedestrian to generate radar detection information; a far-infrared camera sensor configured to imagine heat radiated from the pedestrian to generate far-infrared recognition information; and an information integration processor configured to integrate the radar detection information and the far-infrared recognition information, wherein the PDCMS function includes a collision warning and an activation of an automatic operation of an emergency brake, wherein the electronic control unit is further configured to activate the operation of the PDCMS function, if an initial speed of the pedestrian at a boundary of a driving lane on which the pedestrian is moving is within a first speed range and an initial speed of the vehicle is within a second speed range, the first speed range and the second speed range defining an area in which the PDCMS function is essentially operated.