The effect of electron-beam irradiation (EBI) on MoS2-based photodetectors with various electrode structures was investigated to improve the electrical and photoelectrical properties. The MoS2 films were deposited at room temperature by RF magnetron sputtering and subsequently transformed into a two-dimensional layered structure by EBI treatment with the electron energy of 3 kV for 1 min. The electrical resistance and photoelectrical properties, such as photocurrent and photoresponsivity, of MoS2 films were examined with patterned Au/Ti electrodes as a top contact (TC) and a bottom contact structure. In addition, the interfacial effect of high-k dielectric materials of thin HfO2 film between MoS2 and the SiO2/Si substrate was investigated to enhance the photoelectrical property. The MoS2 photodetectors fabricated by the EBI before TC formation on HfO2 exhibited the highest photoresponsivity of 11.88 mA/W, which was an increase of 6500% from the EBI before TC structure on SiO2. We believe that this work contributes to the improvement of contact and interface properties of MoS2-based photodetectors readily and quickly compared with conventional high-temperature thermal treatment.