A train platform safety device, comprising: a plurality of wire rope lift units installed at selected locations between an inlet of a platform through which a train enters the platform and an outlet of the platform, the wire rope lift units moving wire ropes upwards or downwards; the wire ropes oriented horizontally, the wire ropes connecting the wire rope lift units to each other; and a plurality of wire rope sagging prevention units disposed at positions spaced apart from each other at predetermined intervals between the wire rope lift units so as to prevent the wire ropes from sagging and guide the wire ropes so that the wire ropes smoothly move upwards or downwards, wherein each of the wire rope lift units comprises: a body vertically installed on the ground; a guide vertically provided at a predetermined position of the body; a plurality of blocks installed so as to be movable upwards or downwards along the guide, with the wire ropes connected to predetermined portions of the blocks at positions spaced apart from each other at regular intervals in the vertical direction; a rotating unit rotatably provided at a predetermined position on an upper end or lower end of the body, characterized in that the rotating unit comprises a plurality of rotating members having different diameters, the rotating members being respectively connected to the blocks, wherein the rotating members are rotated or reversely rotated at a same time so as to determine distances that the blocks are moved upwards or downwards such that the wire ropes overlap each other or spread from each other; and a drive unit installed at a predetermined position in the body, the drive unit rotating the rotating unit, wherein a connection means is wound around each rotating member of the rotating unit and connected to a predetermined portion of the corresponding block, and wherein the drive unit comprises: a cylinder installed at a predetermined position in the body; a drive pulley connected to an end of the rotating unit; an interlocking pulley rotatably provided on a rod of the cylinder; and a connector fastened to a portion of the body, the connector being provided around the interlocking pulley and connected to the drive pulley. a plurality of wire rope lift units installed at selected locations between an inlet of a platform through which a train enters the platform and an outlet of the platform, the wire rope lift units moving wire ropes upwards or downwards; the wire ropes oriented horizontally, the wire ropes connecting the wire rope lift units to each other; and a plurality of wire rope sagging prevention units disposed at positions spaced apart from each other at predetermined intervals between the wire rope lift units so as to prevent the wire ropes from sagging and guide the wire ropes so that the wire ropes smoothly move upwards or downwards, wherein each of the wire rope lift units comprises: a body vertically installed on the ground; a guide vertically provided at a predetermined position of the body; a plurality of blocks installed so as to be movable upwards or downwards along the guide, with the wire ropes connected to predetermined portions of the blocks at positions spaced apart from each other at regular intervals in the vertical direction; a rotating unit rotatably provided at a predetermined position on an upper end or lower end of the body, characterized in that the rotating unit comprises a plurality of rotating members having different diameters, the rotating members being respectively connected to the blocks, wherein the rotating members are rotated or reversely rotated at a same time so as to determine distances that the blocks are moved upwards or downwards such that the wire ropes overlap each other or spread from each other; and a drive unit installed at a predetermined position in the body, the drive unit rotating the rotating unit, wherein a connection means is wound around each rotating member of the rotating unit and connected to a predetermined portion of the corresponding block, and wherein the drive unit comprises: a cylinder installed at a predetermined position in the body; a drive pulley connected to an end of the rotating unit; an interlocking pulley rotatably provided on a rod of the cylinder; and a connector fastened to a portion of the body, the connector being provided around the interlocking pulley and connected to the drive pulley.