An ultrasonic Doppler diagnosis device comprising: ultrasonic transceiver means (2, 5) for emitting and scanning an ultrasonic wave and for transmitting and receiving the wave to a kinetic reflector; velocity data calculating means for extracting a Doppler shift signal using an ultrasonic signal from the kinetic reflector transmitted and received by the ultrasonic transceiver means, and for calculating velocity data at an intersection of a sound line and a scanning line of the kinetic reflector; velocity data interpolating means (20, 20a-c) for interpolating the velocity data between the sound line and the scanning line and generating the interpolated velocity data; and color image generating means for generating a color flow mapping image of the kinetic reflector based on the velocity data and the interpolated velocity data, characterized in that the velocity data interpolating means (20, 20a-c) includes numeric value determining means (20a-c) adapted for, when the velocity data interpolating means is interpolating first and second numeric values selected from a plurality of values of the velocity data, converting two scalar arrays of unsigned numeric data corresponding to the first and second numeric values to signed arrays of numeric data, interpolating the signed arrays of numeric data, and reconverting the interpolated signed arrays to scalar arrays, when the first numeric value is a value of 192 to 255 (+π/2 to +π) and the second numeric value is a value of 0 to 63 (-π to -π/2), wherein interpolation of the signed arrays of numeric data is performed based on vector operation on complex spaces in the signed arrays; and interpolating two scalar arrays of unsigned numeric data corresponding to the first and second numeric values when the first numeric value is not a value of 192 to 255 (+π/2 to +π) and the second numeric value is not a value of 0 to 63 (-π to-π/2), wherein interpolation of the unsigned numeric data is performed based on vector operation on complex spaces in the scalar arrays. ultrasonic transceiver means (2, 5) for emitting and scanning an ultrasonic wave and for transmitting and receiving the wave to a kinetic reflector; velocity data calculating means for extracting a Doppler shift signal using an ultrasonic signal from the kinetic reflector transmitted and received by the ultrasonic transceiver means, and for calculating velocity data at an intersection of a sound line and a scanning line of the kinetic reflector; velocity data interpolating means (20, 20a-c) for interpolating the velocity data between the sound line and the scanning line and generating the interpolated velocity data; and color image generating means for generating a color flow mapping image of the kinetic reflector based on the velocity data and the interpolated velocity data, characterized in that the velocity data interpolating means (20, 20a-c) includes numeric value determining means (20a-c) adapted for, when the velocity data interpolating means is interpolating first and second numeric values selected from a plurality of values of the velocity data, converting two scalar arrays of unsigned numeric data corresponding to the first and second numeric values to signed arrays of numeric data, interpolating the signed arrays of numeric data, and reconverting the interpolated signed arrays to scalar arrays, when the first numeric value is a value of 192 to 255 (+π/2 to +π) and the second numeric value is a value of 0 to 63 (-π to -π/2), wherein interpolation of the signed arrays of numeric data is performed based on vector operation on complex spaces in the signed arrays; and interpolating two scalar arrays of unsigned numeric data corresponding to the first and second numeric values when the first numeric value is not a value of 192 to 255 (+π/2 to +π) and the second numeric value is not a value of 0 to 63 (-π to-π/2), wherein interpolation of the unsigned numeric data is performed based on vector operation on complex spaces in the scalar arrays.