A tape feeder comprising: a sprocket with teeth , the teeth configured to engage with feeding holes of component supply tape in which many components are arranged at a specified pitch, and the sprocket being rotated by a motor such that the component supply tape is fed intermittently by the specified pitch so that the components in the component supply tape can be picked up one by one by a suction nozzle of a component mounter ; a magnetic member configured to rotate together with the sprocket ; a magnetic field detecting element arranged at a position facing a rotation region of the magnetic member and configured to output a signal in accordance with a magnetic field of the magnetic member ; a rotation angle detecting means configured to process the output signal of the magnetic field detecting element to detect a rotation degree of the sprocket in terms of an absolute angle; and a control means configured to control pitch feeding operation of the sprocket by the motor , the control means which is configured to correct the pitch feeding amount of the motor based on the rotation angle of the sprocket detected by the rotation angle detecting means for each pitch feeding operation of the sprocket immediately after the motor is started, characterized in that : the control means is provided with a means for determining whether checking of the rotation state of the sprocket is required based on the rotation angle of the sprocket detected by the rotation angle detecting means , wherein the control means is provided with a means for reporting to an operator when it is determined that it is necessary to check the rotation state of the sprocket . a sprocket with teeth , the teeth configured to engage with feeding holes of component supply tape in which many components are arranged at a specified pitch, and the sprocket being rotated by a motor such that the component supply tape is fed intermittently by the specified pitch so that the components in the component supply tape can be picked up one by one by a suction nozzle of a component mounter ; a magnetic member configured to rotate together with the sprocket ; a magnetic field detecting element arranged at a position facing a rotation region of the magnetic member and configured to output a signal in accordance with a magnetic field of the magnetic member ; a rotation angle detecting means configured to process the output signal of the magnetic field detecting element to detect a rotation degree of the sprocket in terms of an absolute angle; and a control means configured to control pitch feeding operation of the sprocket by the motor , the control means which is configured to correct the pitch feeding amount of the motor based on the rotation angle of the sprocket detected by the rotation angle detecting means for each pitch feeding operation of the sprocket immediately after the motor is started, characterized in that : the control means is provided with a means for determining whether checking of the rotation state of the sprocket is required based on the rotation angle of the sprocket detected by the rotation angle detecting means , wherein the control means is provided with a means for reporting to an operator when it is determined that it is necessary to check the rotation state of the sprocket . the control means is provided with a means for determining whether checking of the rotation state of the sprocket is required based on the rotation angle of the sprocket detected by the rotation angle detecting means , wherein the control means is provided with a means for reporting to an operator when it is determined that it is necessary to check the rotation state of the sprocket . <EOS>