Provided is a spun-bonded nonwoven fabric including fibers formed of a resin composition that contains: a propylene polymer (A); and a polymer (B) which is at least one selected from the group consisting of polyolefins, other than the propylene polymer (A), and polyesters. The fibers have a sea-island structure. The fibers include fibers in which a ratio of island phases having a diameter of less than 0.32 μm among those island phases at a cross-section perpendicular to the axial direction of the fibers is 60% or higher on a number basis. In the spun-bonded nonwoven fabric, a ratio (SMB/SCB) of the tensile strength (SMD) in a machine flow direction (MD) with respect to the tensile strength (SCD)) in a direction (CD) perpendicular to the machine flow direction (MD) is from 2.0 to 5.1.