To obtain a non-crimped shortcut acrylic synthetic fiber that does not form a fiber ball even in a process after shortcutting of a non-crimped part of an acrylic synthetic fiber and is uniformly dispersed into water.

The non-crimped shortcut acrylic synthetic fiber has 1 mm-10 mm fiber length and 0.5 wt.%-2 wt.% coating weight of a finishing oil composition including a water-soluble polymer. A material having ≥40% of acrylonitrile is especially preferably used as the acrylic synthetic fiber.