A squaring multiplier for a floating-point number comprises: a pseudo carry generator for generating pseudo information concerning a carry equivalent to predetermined bits for the calculation of a target variable; an MSB look ahead circuit for employing the variable to perform a look ahead operation and establish the location of the MSB (Most Significant Bit) in the calculation results; and combinational circuits for performing the rounding off process and the calculation of the variables by using information concerning a carry, which is generated by the pseudo carry generator and based on the location of the MSB determined by the MSB look ahead circuit.