A method and an apparatus for measuring an inclination angle of an ion beam when ions are implanted into a semiconductor wafer include an ion current measuring section having a Faraday cup assembly which is rotatably installed, an angle varying section for adjusting an alignment angle of the Faraday cup assembly, and an inclination angle measuring section for measuring the inclination angle of the ion beam based on a variation of the ion current caused by a variation of the alignment angle of the Faraday cup assembly. By measuring the inclination angle of the ion beam, the incident angle of the ion beam, which is incident into the wafer during the ion implantation process, can be precisely adjusted to a predetermined critical angle. Accordingly, the channeling effect and shadow effect can be effectively prevented. The amount of the ions included in the ion beam can be precisely measured, so the amount of ions implanted into the wafer can be precisely adjusted.