Abstract: An object of the present invention is to provide a purification column which is a small purification column in which a volume of a liquid to be treated is reduced in order to reduce the amount of blood to be taken out and which realizes a low pressure loss and has high adsorption performance. The present invention provides a fiber bundle including a plurality of porous fibers that satisfies the following requirements (A) to (E): (A) the porous fiber has a non-hollow shape, (B) an arithmetic average roughness (dry Ra value) of a surface of the porous fiber in a dry state is 11 nm or more and 30 nm or less, (C) an arithmetic average roughness (wet Ra value) of a surface of the porous fiber in a wet state is 12 nm or more and 40 nm or less, (D) a value represented by wet Ra/dry Ra is 1.05 or more, and (E) a linear rate of the fiber bundle represented by (length of fiber bundle)/(length of one porous fiber) is 0.97 or more and 1.00 or less.