A gas sensor for detecting a predetermined gas component in a measurement gas, said gas sensor comprising: a sensor element mainly containing solid electrolyte with oxygen ion conductivity; and a protective cover arranged to surround said sensor element, wherein said protective cover includes an inner protective cover of a bottomed cylindrical shape that has a plurality of inner gas distributing holes formed in two rows on a side surface of said inner protective cover in a longitudinal direction of said sensor element and surrounds one end of said sensor element, and an outer protective cover of a bottomed cylindrical shape that has a plurality of outer gas distributing holes on a side surface of said outer protective cover and surrounds said inner protective cover, wherein said plurality of inner gas distributing holes has a plurality of first inner gas distributing holes and a plurality of second inner gas distributing holes, said plurality of first inner gas distributing holes is formed on the side surface of said inner protective cover in a position on a bottom side of said inner protective cover with respect to a position opposed to one front end of said sensor element, said plurality of second inner gas distributing holes is formed on the side surface of said inner protective cover in a position on an other front end of said sensor element with respect to the position opposed to the one front end of said sensor element, and when a total opening area of said plurality of first the inner gas distributing holes is determined as S1 and a total opening area of said plurality of second inner gas distributing holes is determined as S2, S 1 / S 2 ≤ 0.44. a sensor element mainly containing solid electrolyte with oxygen ion conductivity; and a protective cover arranged to surround said sensor element, wherein said protective cover includes an inner protective cover of a bottomed cylindrical shape that has a plurality of inner gas distributing holes formed in two rows on a side surface of said inner protective cover in a longitudinal direction of said sensor element and surrounds one end of said sensor element, and an outer protective cover of a bottomed cylindrical shape that has a plurality of outer gas distributing holes on a side surface of said outer protective cover and surrounds said inner protective cover, wherein said plurality of inner gas distributing holes has a plurality of first inner gas distributing holes and a plurality of second inner gas distributing holes, said plurality of first inner gas distributing holes is formed on the side surface of said inner protective cover in a position on a bottom side of said inner protective cover with respect to a position opposed to one front end of said sensor element, said plurality of second inner gas distributing holes is formed on the side surface of said inner protective cover in a position on an other front end of said sensor element with respect to the position opposed to the one front end of said sensor element, and when a total opening area of said plurality of first the inner gas distributing holes is determined as S1 and a total opening area of said plurality of second inner gas distributing holes is determined as S2, S 1 / S 2 ≤ 0.44.