A wrench includes a hollow handle, a driver, a battery base, an alert device, a switch and a force applying device. The driver includes a drive shaft and a drive head. The drive shaft is received in the hollow handle and pivotally connected to the inner wall of the hollow handle. The drive head is connected to the drive shaft and protrudes from the hollow handle. The switch electrically connects the battery base and the alert device. The switch includes a first contact and a second contact. The first contact is located on the drive shaft. The second contact is located on the inner wall of the hollow handle. The force applying device applies a predetermined force to the drive shaft to separate the first contact and the second contact.