A control device for a transmission including m (m ≥ 3) solenoid valves and configured to establish a plurality of shift speeds by engaging n1 (2 ≤ n1 < m) engagement elements using hydraulic pressures of n1 solenoid valves among the m solenoid valves, the control device comprising: current threshold setting means for setting respective currents to be applied to solenoids of n2 (n1 < n2 ≤ m) solenoid valves corresponding to n2 engagement elements at the time when braking torque acts on an output shaft of the transmission with the n2 engagement elements engaged as current thresholds; and determination means for determining whether or not braking torque is generated on the output shaft of the transmission by comparing respective current values to be applied to the solenoids of the n2 solenoid valves and the set current thresholds corresponding to the solenoids of the n2 solenoid valves, characterized in that the n2 is a value that is larger than the n1 by a value of 1, and the current threshold setting means performs the current threshold setting process by setting predetermined-time assumed drag torque, which serves as drag torque assumed to be generated by engagement of the subject element when the n2 determination elements are engaged, on the basis of a first speed change ratio, a second speed change ratio, and torque input to an input shaft of the transmission, the first speed change ratio being a ratio in rotational speed between the input shaft and the output shaft of the transmission at the time when n1 non-subject elements, which are n1 of the n2 determination elements excluding the subject element, are engaged, and the second speed change ratio being a ratio between a subject element rotational speed difference, which is a difference in rotational speed between an input side and an output side of the subject element, and a rotational speed of the output shaft of the transmission at the time when the n1 non-subject elements are engaged, and setting a current applied to a solenoid of the subject valve corresponding to the set predetermined-time assumed drag torque as the current threshold. current threshold setting means for setting respective currents to be applied to solenoids of n2 (n1 < n2 ≤ m) solenoid valves corresponding to n2 engagement elements at the time when braking torque acts on an output shaft of the transmission with the n2 engagement elements engaged as current thresholds; and determination means for determining whether or not braking torque is generated on the output shaft of the transmission by comparing respective current values to be applied to the solenoids of the n2 solenoid valves and the set current thresholds corresponding to the solenoids of the n2 solenoid valves, characterized in that the n2 is a value that is larger than the n1 by a value of 1, and the current threshold setting means performs the current threshold setting process by setting predetermined-time assumed drag torque, which serves as drag torque assumed to be generated by engagement of the subject element when the n2 determination elements are engaged, on the basis of a first speed change ratio, a second speed change ratio, and torque input to an input shaft of the transmission, the first speed change ratio being a ratio in rotational speed between the input shaft and the output shaft of the transmission at the time when n1 non-subject elements, which are n1 of the n2 determination elements excluding the subject element, are engaged, and the second speed change ratio being a ratio between a subject element rotational speed difference, which is a difference in rotational speed between an input side and an output side of the subject element, and a rotational speed of the output shaft of the transmission at the time when the n1 non-subject elements are engaged, and setting a current applied to a solenoid of the subject valve corresponding to the set predetermined-time assumed drag torque as the current threshold.