A slide door apparatus for a vehicle, comprising: a driving device adapted to be mounted to a slide door supported by a vehicle body for opening and closing an opening formed at the vehicle body; a guide pulley unit adapted to be mounted to the slide door and including a plurality of guide pulleys (43, 44) each having a first guide groove (48a, 44b) and a second guide groove (48a, 44a) arranged axially in parallel to each other, the guide pulley unit further including a first housing member and a second housing member for housing the plurality of guide pulleys (43, 44) to be rotatable therein; a guiding rail adapted to be mounted to the vehicle body; and a supporting member adapted to be pivotably connected to the slide door and slidably guided by the guiding rail, wherein the guide pulley unit is mounted to the supporting member to guide a cable (22, 23) in accordance with a pivotal movement of the slide door relative to the supporting member by means of the plurality of guide pulleys (43, 44); wherein the cable is connected to the driving device to be wound to and unwound from the driving device, the cable including a first portion disposed into the first groove (48a, 44b) of each of the plurality of guide pulleys (43, 44) and an end of the first portion adapted to be connected to the vehicle body at a first side in a moving direction of the slide door, the cable further including a second portion disposed into the second groove (47a, 44a) of each of the plurality of guide pulleys (43, 44) and an end of the second portion adapted to be connected to the vehicle body at a second side in the moving direction of the slide door; and a separating member provided between the first and second housing members (41, 42), characterized in that the separating member is provided for separating said first portion of said cable disposed in said first guide groove of said plurality of the guide pulleys from said second portion of said cable disposed in said second guide grooves (48a, 47a, 44b, 44a) of said plurality of the guide pulleys (43, 44), so that said first and second portions of cable are prevented from crossing or interfering each other, wherein the separating member includes a body portion extending in a direction perpendicular to an axial direction of the plurality of guide pulleys (43, 44) and a plurality of leg portions (45c, 45d, 45e) extending from the body portion to make contact with at least one of the first and second housing member (41, 42) and supporting the body portion at an axial position between the first and second guide grooves (48a, 47a, 44b, 44a) of each of the plurality of guide pulleys (43, 44). a driving device adapted to be mounted to a slide door supported by a vehicle body for opening and closing an opening formed at the vehicle body; a guide pulley unit adapted to be mounted to the slide door and including a plurality of guide pulleys (43, 44) each having a first guide groove (48a, 44b) and a second guide groove (48a, 44a) arranged axially in parallel to each other, the guide pulley unit further including a first housing member and a second housing member for housing the plurality of guide pulleys (43, 44) to be rotatable therein; a guiding rail adapted to be mounted to the vehicle body; and a supporting member adapted to be pivotably connected to the slide door and slidably guided by the guiding rail, wherein the guide pulley unit is mounted to the supporting member to guide a cable (22, 23) in accordance with a pivotal movement of the slide door relative to the supporting member by means of the plurality of guide pulleys (43, 44); wherein the cable is connected to the driving device to be wound to and unwound from the driving device, the cable including a first portion disposed into the first groove (48a, 44b) of each of the plurality of guide pulleys (43, 44) and an end of the first portion adapted to be connected to the vehicle body at a first side in a moving direction of the slide door, the cable further including a second portion disposed into the second groove (47a, 44a) of each of the plurality of guide pulleys (43, 44) and an end of the second portion adapted to be connected to the vehicle body at a second side in the moving direction of the slide door; and a separating member provided between the first and second housing members (41, 42), characterized in that the separating member is provided for separating said first portion of said cable disposed in said first guide groove of said plurality of the guide pulleys from said second portion of said cable disposed in said second guide grooves (48a, 47a, 44b, 44a) of said plurality of the guide pulleys (43, 44), so that said first and second portions of cable are prevented from crossing or interfering each other, wherein the separating member includes a body portion extending in a direction perpendicular to an axial direction of the plurality of guide pulleys (43, 44) and a plurality of leg portions (45c, 45d, 45e) extending from the body portion to make contact with at least one of the first and second housing member (41, 42) and supporting the body portion at an axial position between the first and second guide grooves (48a, 47a, 44b, 44a) of each of the plurality of guide pulleys (43, 44).