In a well array filter (1), a plurality of wells (3) are formed in a filter body (2), the wells (3) adjacent to each other are separated by a well partition wall (6), two or more through-holes (8) are formed in a well bottom portion (4), the minimum width of the opening of the through-hole (8) is 1 m or more and 3.5 m or less, and the ratio of a total opening area of the through-hole is 0.5% or more and 3.5% or less. Assuming a minimum circumscribed circle (G1) that surrounds all of the through-holes (8) in each well bottom portion (4), when the center is moved to the center of each of the plurality of through-holes (8), all minimum circumscribed circles (G2) after movement at least partially overlap all of the plurality of through-holes (8).