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 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 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 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 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.