The invention relates to a method and an apparatus for treating plant based raw material with an enzymatic hydrolysis, in which the plant based raw material (1) is treated to form lignocellulosic material (3a,3b) and the lignocellulosic material (3a,3b) or its fraction (10) is conducted into the enzymatic hydrolysis (4), wherein the method comprises at least one treatment stage (2a,2b,2c) in which the plant based raw material (1) is treated so that the lignocellulosic material (3a,3b) contains over 80% fine solid particles which are fiber-like or indefinable particles smaller than 0.2 mm, defined by an optical measurement device, the lignocellulosic material (3a,3b) or at least one fraction (10) of the lignocellulosic material is supplied into the enzymatic hydrolysis (4) for forming a lignin based material (5), and at least one solid-liquid separation stage (6) after the enzymatic hydrolysis (4) in which a lignin fraction (7) and a soluble carbohydrate containing fraction (8) are separated. Further, the invention relates to the soluble carbohydrate containing fraction, the lignin fraction, the lignin based material, the liquid fraction and the solid fraction, and their uses.