An electric screwdriver controller having a function for determining that a correct tightening operation has been carried out when said tightening operation has taken a time longer than a reference time, said controller comprising: a torque monitoring means for monitoring whether or not a load torque in carrying out a tightening operation by using an electric screwdriver has reached a tightening completion torque indicating a completion of the tightening operation; a timer means for measuring a time interval from a starting time of the tightening operation to a time when the tightening torque has reached the tightening completion torque, as a tightening operation time; and a means for determining a reference time for a subsequent tightening operation based on a plurality of tightening operation times obtained from said timer means in the tightening operations carried out for a predetermined number of screws; said electric screwdriver controller being characterized in that said means for determining a reference time comprises: an expected time setting means for setting an expected time from the starting time to the completion time of the tightening operation; a comparing means for comparing the tightening operation time obtained from said timer means to said expected time for each of the tightening operations; and an expected time renewing means operable, when a comparison result indicating that the tightening operation time is not longer than the expected time is given by said comparing means, to renew said expected time by replacing said expected time with said tightening operation time, wherein the expected time obtained from the expected time renewing means at the time of completion of the tightening operations for the predetermined number of screws is taken as said reference time. a torque monitoring means for monitoring whether or not a load torque in carrying out a tightening operation by using an electric screwdriver has reached a tightening completion torque indicating a completion of the tightening operation; a timer means for measuring a time interval from a starting time of the tightening operation to a time when the tightening torque has reached the tightening completion torque, as a tightening operation time; and a means for determining a reference time for a subsequent tightening operation based on a plurality of tightening operation times obtained from said timer means in the tightening operations carried out for a predetermined number of screws; said electric screwdriver controller being characterized in that said means for determining a reference time comprises: an expected time setting means for setting an expected time from the starting time to the completion time of the tightening operation; a comparing means for comparing the tightening operation time obtained from said timer means to said expected time for each of the tightening operations; and an expected time renewing means operable, when a comparison result indicating that the tightening operation time is not longer than the expected time is given by said comparing means, to renew said expected time by replacing said expected time with said tightening operation time, wherein the expected time obtained from the expected time renewing means at the time of completion of the tightening operations for the predetermined number of screws is taken as said reference time. an expected time setting means for setting an expected time from the starting time to the completion time of the tightening operation; a comparing means for comparing the tightening operation time obtained from said timer means to said expected time for each of the tightening operations; and an expected time renewing means operable, when a comparison result indicating that the tightening operation time is not longer than the expected time is given by said comparing means, to renew said expected time by replacing said expected time with said tightening operation time, the expected time obtained from the expected time renewing means at the time of completion of the tightening operations for the predetermined number of screws is taken as said reference time.