Most research on assembly sequencing considered sequential execution of assembly tasks. However, the need of parallel execution of assembly tasks increases as the time and space for generating products become major factors in determining the cost of the products. This paper presents a method for generating assembly sequences that allows parallel execution of assembly tasks at a workplace as well as between the workplaces. To increase the efficiency in generating the assembly sequences, assembly constraints which are caused by the geometry of parts and the contact relationship between the parts are acquired explicitly in simplified form.