An eyeglass lens processing apparatus, comprising: a grinding wheel mounted frame mounted with a grinding wheel for grinding a lens, and whose position is changed according to a predetermined grinding depth of the lens; a carriage for moving the lens to contact with the grinding wheel , and which contacts with the grinding wheel mounted frame when the lens which contacts with the grinding wheel is grinded to the predetermined grinding depth; and a hall sensor detector for detecting a contact of the grinding wheel mounted frame and the carriage , wherein the hall sensor detector includes a magnet and a hall sensor for detecting an intensity of a magnetic field generated by the magnet , the magnet is equipped on either one of the carriage and the grinding wheel mounted frame , and the hall sensor is equipped on the other one of the carriage and the grinding wheel mounted frame , wherein the eyeglass lens processing apparatus comprises a processing unit configured to define a reference output signal (A0) of the hall sensor when the grinding wheel mounted frame and the carriage are in contacts with each other at a grinding direction, and if an output signal of the hall sensor is smaller or larger than the reference output signal (A0) within a tolerance (a), it is determined that the grinding wheel mounted frame and the carriage are in a contact state, characterized in that the processing unit updates at every grinding direction the reference output signal of the hall sensor and the reference output signal obtained at a grinding direction is used as the new reference output signal to determine whether the grinding wheel mounted frame is in contacts with the carriage at a next grinding direction. a grinding wheel mounted frame mounted with a grinding wheel for grinding a lens, and whose position is changed according to a predetermined grinding depth of the lens; a carriage for moving the lens to contact with the grinding wheel , and which contacts with the grinding wheel mounted frame when the lens which contacts with the grinding wheel is grinded to the predetermined grinding depth; and a hall sensor detector for detecting a contact of the grinding wheel mounted frame and the carriage , wherein the hall sensor detector includes a magnet and a hall sensor for detecting an intensity of a magnetic field generated by the magnet , the magnet is equipped on either one of the carriage and the grinding wheel mounted frame , and the hall sensor is equipped on the other one of the carriage and the grinding wheel mounted frame , wherein the eyeglass lens processing apparatus comprises a processing unit configured to define a reference output signal (A0) of the hall sensor when the grinding wheel mounted frame and the carriage are in contacts with each other at a grinding direction, and if an output signal of the hall sensor is smaller or larger than the reference output signal (A0) within a tolerance (a), it is determined that the grinding wheel mounted frame and the carriage are in a contact state, characterized in that the processing unit updates at every grinding direction the reference output signal of the hall sensor and the reference output signal obtained at a grinding direction is used as the new reference output signal to determine whether the grinding wheel mounted frame is in contacts with the carriage at a next grinding direction. <EOS>