An electric linear actuator has a housing, an electric motor, a speed reduction mechanism, and a ball screw mechanism. The ball screw mechanism has a nut and a screw shaft. Both include a helical screw groove. The nut is supported by rolling bearings mounted on the housing. The screw shaft is coaxially integrated with the drive shaft. The screw shaft is inserted into the nut, via a large number of balls. The housing has a first housing and a second housing. The electric motor is mounted on the first housing. The second housing abuts against an end face of the first housing. At least one of the first and second housings is formed with ribs. The ribs extend from each of securing portions to a containing portion that contains the screw shaft. The securing portions are arranged on the periphery of the housing to receive fastening bolts.