Arithmetic Logic Unit (ALU) is the essential part of the Central Processing Unit (CPU) core which performs arithmetical operations such as addition, subtraction, division, multiplication etc., logical operations such as and, or, xor etc. and shift rotate operations. The CPU performance is directly related to the performance of ALU. In this study, the 64 bit ALU has been designed by using the Very High Speed Integrated Circuits Hardware Description Language (VHDL) and Altera Field Programmable Gate Array (FPGA) families, synthesized and simulated with the help of Altera Quartus II (Intel, Santa Clara, CA, USA) v13.0sp1 and Modelsim-Altera v10.1d (Intel, Santa Clara, CA, USA) software. Many different studies are given about ALU Design and Implementation with the use of FPGA architecture and VHDL language. The difference of this study from recent studies is that the proposed design allows the processing of the signed numbers. Also, Conditional Sum Adder (COSA) is used in addition operation instead of Carry Ripple Adder (CRA) or Carry Look ahead Adder (CLA) because of its benefit in fast addition and less propagation delay of Carry Chain.