A walking condition determining device for determining a walking condition of a walker having a plurality of legs, comprising: a measuring means comprising a first measuring means for measuring a first parameter (x 1) and a second measuring means for measuring a second parameter (x 2); a first storage means for storing a plurality of regions in a two-dimensional space corresponding to the first and second parameters and a plurality of walking conditions of the walker such that they are associated with each other; a generating means for generating a plot defined in the two-dimensional space by the first and second parameters measured by the measuring means; and a determining means for determining a walking condition of the walker on the basis of the plot generated by the generating means; characterised in that: the first measuring means is configured to measure an amount of variation in a vertical interval of a foot joint with respect to a hip joint of a leg of the walker in comparison with an upright state in which the hip, knee and foot joints,, are on a vertical line as the first parameter; the second measuring means is configured to measure an amount of variation in the longitudinal direction of the foot joint with respect to the hip joint in comparison with the upright state as the second parameter; and the determining means is configured to determine that the walker is in a normal walking condition if an entire plot in the two-dimensional space exists in a first region wherein the first parameter (x 1) is below a predetermined threshold value (c), whereas it is configured to determine that the walker is in a slope walking condition if at least part of the plot exists in a second region wherein the first parameter (x 1) is the predetermined threshold value (c) or more. a measuring means comprising a first measuring means for measuring a first parameter (x 1) and a second measuring means for measuring a second parameter (x 2); a first storage means for storing a plurality of regions in a two-dimensional space corresponding to the first and second parameters and a plurality of walking conditions of the walker such that they are associated with each other; a generating means for generating a plot defined in the two-dimensional space by the first and second parameters measured by the measuring means; and a determining means for determining a walking condition of the walker on the basis of the plot generated by the generating means; characterised in that: the first measuring means is configured to measure an amount of variation in a vertical interval of a foot joint with respect to a hip joint of a leg of the walker in comparison with an upright state in which the hip, knee and foot joints,, are on a vertical line as the first parameter; the second measuring means is configured to measure an amount of variation in the longitudinal direction of the foot joint with respect to the hip joint in comparison with the upright state as the second parameter; and the determining means is configured to determine that the walker is in a normal walking condition if an entire plot in the two-dimensional space exists in a first region wherein the first parameter (x 1) is below a predetermined threshold value (c), whereas it is configured to determine that the walker is in a slope walking condition if at least part of the plot exists in a second region wherein the first parameter (x 1) is the predetermined threshold value (c) or more.