A method of modulating data, which is represented by two data types of ‘high’ and ‘low’, and demodulating the modulated data, is disclosed. In a method of data modulation and demodulation for a communication system which has a transmitting end modulating a data and a receiving end demodulating the transmitted data from the transmitting end, the data is represented by two types including ‘high’ and ‘low’, and the receiving end receives at least one data which consists of at least one code-word spread by a unique orthogonal code. The receiving end adds up the received data in the unit of code-word, and subtracts the length of the orthogonal code from a value which is obtained by doubling the sum of the code-word, when the code-word of the orthogonal code is ‘0’. The receiving end then averages the result after the subtraction in the unit of orthogonal code length and extracts the result, and therefore, obtains the data from the transmitting end.