The present invention relates to novel cephalosporin derivatives represented by Chemical Formula 1. Wherein, X, Y, L, R 1 , and R 2 are as same as defined in the description of the invention. The present invention also relates to pharmaceutical antibiotic compositions comprising a novel celphalosporin derivative represented by Chemical Formula 1, a prodrug thereof, a hydrate thereof, a solvate thereof, an isomer thereof, or a pharmaceutically acceptable salt thereof as an effective ingredient. According to the present invention, novel cephalosporin derivatives, a prodrug thereof, a hydrate thereof, a solvate thereof, an isomer thereof, or a pharmaceutically acceptable salt thereof as an effective ingredient for the broad spectrum of antibiotic resistant, low toxicity, particularly in Gram-negative bacteria, which can be useful with strong antimicrobial activity.