A road surface condition estimation apparatus comprising: a collecting device that is configured to collect, from each of a plurality of vehicles, behavior information relating to a behavior of each vehicle; a determining device that is configured to determine on the basis of the behavior information whether or not an abnormality condition is satisfied, the abnormality condition being set on the basis of a specific behavior, the specific behavior being a behavior expected to be taken by the vehicle when the vehicle encounters a road surface abnormality, the road surface abnormality including at least one of a defect of a road surface and an obstacle on the road surface; an estimating device that is configured to estimate a condition of the road surface on the basis of a determined result of the determining device; characterised in that the specific behavior includes a second specific behavior that the vehicle travels on a position of the road surface abnormality with the vehicle being affected by the road surface abnormality, the behavior information includes an input information relating to an input from the road surface to the vehicle, the determining device is configured to extract, from the input information, an up-and-down component caused by concavity and / or convexity at the road surface and calculate an index value representing a degree of the concavity and / or the convexity at the road surface on the basis of the up-and-down component, the abnormality condition includes a third abnormality condition that an average value of the index value at one point on a road is equal to or larger than a first predetermined value, and a fourth abnormality condition that a maximum value of the index value at the one point on the road is equal to or larger than a second threshold value that is larger than the first predetermined value, the estimating device is configured to estimate that there exists roughness of the road surface as the road surface abnormality at the one point, when it is determined that the third abnormality condition is satisfied, and to estimate that there exists local concavity and / or convexity as the road surface abnormality at the one point, when it is determined that the fourth abnormality condition is satisfied. a collecting device that is configured to collect, from each of a plurality of vehicles, behavior information relating to a behavior of each vehicle; a determining device that is configured to determine on the basis of the behavior information whether or not an abnormality condition is satisfied, the abnormality condition being set on the basis of a specific behavior, the specific behavior being a behavior expected to be taken by the vehicle when the vehicle encounters a road surface abnormality, the road surface abnormality including at least one of a defect of a road surface and an obstacle on the road surface; an estimating device that is configured to estimate a condition of the road surface on the basis of a determined result of the determining device; characterised in that the specific behavior includes a second specific behavior that the vehicle travels on a position of the road surface abnormality with the vehicle being affected by the road surface abnormality, the behavior information includes an input information relating to an input from the road surface to the vehicle, the determining device is configured to extract, from the input information, an up-and-down component caused by concavity and / or convexity at the road surface and calculate an index value representing a degree of the concavity and / or the convexity at the road surface on the basis of the up-and-down component, the abnormality condition includes a third abnormality condition that an average value of the index value at one point on a road is equal to or larger than a first predetermined value, and a fourth abnormality condition that a maximum value of the index value at the one point on the road is equal to or larger than a second threshold value that is larger than the first predetermined value, the estimating device is configured to estimate that there exists roughness of the road surface as the road surface abnormality at the one point, when it is determined that the third abnormality condition is satisfied, and to estimate that there exists local concavity and / or convexity as the road surface abnormality at the one point, when it is determined that the fourth abnormality condition is satisfied.