A motor cycle brake controlling apparatus for a motorcycle of the by-wire type wherein an operation amount applied to each of brake operation means (19f, 19r) for front and rear wheels (11f, 11r) is detected by an electronic control unit and fluid pressures are generated by fluid pressure modulators (21f, 21r) for the front and rear wheels (11f, 11r) based on the detection values and then braking force is generated for brake apparatus (20f, 20r) for the front and rear wheels (11f, 11r) by the fluid pressures, wherein said electronic control unit causes said brake apparatus (20f, 20r) for the front and rear wheels (11f, 11r) to carry out control of: causing, when said brake operation means for the front wheel is operated, said brake apparatus for the front wheel to generate braking force for the front wheel in response to an operation amount of said brake operation means for the front wheel and causing said brake apparatus for the rear wheel, when said brake operation means of the rear wheel is not operated, to generate braking force for the rear wheel which interlocks with the operation amount of said brake operation means for the front wheel; characterized by said electronic control unit further causing, in a first mode within a first mode first interval or in a second mode within a second mode first interval wherein in these first intervals the operation amount of said brake operation means of the front wheel changes from zero to a first mode first predetermined value or a second mode first predetermined value respectively, the braking force for the front wheel to increase gradually and causing the braking force for the rear wheel to gradually increase irrespective of a brake operation of the rear wheel break operation means; gradually increasing, in the first mode within a first mode second interval or in the second mode within a second mode second interval wherein in these second intervals the operation amount of said brake operation means of the front wheel changes from the respective first mode first predetermined value or second mode first predetermined value to a first mode second predetermined value or a second mode second predetermined value higher than the respective first predetermined value, the braking force for the front wheel and keeping the braking force for the rear wheel to a maximum value (F1, F2) in the respective first interval; in the first mode, keeping the increasing rate of the breaking force for the front wheel constant throughout the first and second interval; and in the second mode, increasing or decreasing, from an intermediate point (pm) included in a range from a start point of the second mode first interval to an end point of the second mode second interval, the increasing rate of the braking force for the front wheel with respect to the operation amount of the brake operation means of the front wheel to increase or decrease the deceleration of the vehicle so as to vary substantially linearly with respect to an increase of the braking force of the brake for the front wheel. causing, when said brake operation means for the front wheel is operated, said brake apparatus for the front wheel to generate braking force for the front wheel in response to an operation amount of said brake operation means for the front wheel and causing said brake apparatus for the rear wheel, when said brake operation means of the rear wheel is not operated, to generate braking force for the rear wheel which interlocks with the operation amount of said brake operation means for the front wheel;