The present small swing type excavator is characterized by comprising an engine (81) disposed in the rear section of a rotating frame (8) in such a condition that the longitudinal direction thereof is directed to the lateral direction of the rotating frame (8), a hydraulic oil tank (82) disposed on one lateral side in front of the engine (81), a cabin (83) disposed on the other lateral side, an air conditioner (85) disposed under a floor (84) of the cabin (83) and having two surfaces facing to, respectively, the front side and the left outer side of the rotating frame (8), and a fuel tank (86) formed so as to be arranged along at least two surfaces of the front and left side surfaces of the air conditioner (85) and detachably attached to the rotating frame (8).