A seat slide apparatus for a vehicle, comprising: first and second lower rails arranged at both sides in a width direction of a seat and extending in a longitudinal direction of the seat; first and second upper rails fixed to the seat and movably connected to the first and second lower rails respectively in the longitudinal direction; first and second lock levers rotatably connected to the first and second upper rails respectively, the first and second lock levers engaging with the first and second lower rails respectively to selectively restrict a movement of the first and second upper rails relative to the first and second lower rails; first and second biasing members biasing the first and second lock levers respectively in such a manner that the movement of the first and second upper rails relative to the first and second lower rails is restricted; first and second support brackets fixed to the first and second upper rails and including first and second support portions respectively; an operation handle integrally including an operating portion that extends in the width direction and first and second power transmission portions extending in the longitudinal direction from both ends of the operating portion to be supported by the first and second support portions, the first and second power transmission portions pressing the first and second lock levers respectively in association with rotations of the first and second power transmission portions relative to the first and second support portions so as to release the restriction of the movement of the first and second upper rails relative to the first and second lower rails by the first and second lock levers against a biasing force of the first and second biasing members; and a release lever rotatably connected to the first upper rail, characterized in that the release lever is positioned away from the first power transmission portion in a state where a seat back returns from a forward folding state and rotates in association with a forward folding of the seat back of the seat so as to release the restriction of the movement of the first and second upper rails relative to the first and second lower rails by the first and second lock levers by directly pressing the first power transmission portion. first and second lower rails arranged at both sides in a width direction of a seat and extending in a longitudinal direction of the seat; first and second upper rails fixed to the seat and movably connected to the first and second lower rails respectively in the longitudinal direction; first and second lock levers rotatably connected to the first and second upper rails respectively, the first and second lock levers engaging with the first and second lower rails respectively to selectively restrict a movement of the first and second upper rails relative to the first and second lower rails; first and second biasing members biasing the first and second lock levers respectively in such a manner that the movement of the first and second upper rails relative to the first and second lower rails is restricted; first and second support brackets fixed to the first and second upper rails and including first and second support portions respectively; an operation handle integrally including an operating portion that extends in the width direction and first and second power transmission portions extending in the longitudinal direction from both ends of the operating portion to be supported by the first and second support portions, the first and second power transmission portions pressing the first and second lock levers respectively in association with rotations of the first and second power transmission portions relative to the first and second support portions so as to release the restriction of the movement of the first and second upper rails relative to the first and second lower rails by the first and second lock levers against a biasing force of the first and second biasing members; and a release lever rotatably connected to the first upper rail, characterized in that the release lever is positioned away from the first power transmission portion in a state where a seat back returns from a forward folding state and rotates in association with a forward folding of the seat back of the seat so as to release the restriction of the movement of the first and second upper rails relative to the first and second lower rails by the first and second lock levers by directly pressing the first power transmission portion.