A review on the Minimal Supersymmetric Standard Model (MSSM) is given, putting a special emphasis on the Higgs sector. The electroweak symmetry breaking in the context of the MSSM is analyzed. It is found that there are five Higgs bosons in the model, and their tree-level masses are determined. However these masses receive quantum corrections, which can be large if the particles involved in the loop diagrams have large masses. In this thesis, the one-loop correction, due to the top quark and stop squark loops, to the Higgs effective potential is obtained. It is found that such a one-loop correction changes the upper bound on the mass of the lightest Higgs boson substantially with the known value of top quark mass and a sufficiently high supersymmetry breaking scale.