The invention provides an interactive circuit designing apparatus wherein a logic design, a layout design and a speed analysis can cooperate with each other in processing. The interactive circuit designing apparatus comprises a logical designing section for logically designing a design object circuit, a layout designing section for performing mounting arrangement of logical components constituting a design object circuit based on a result of the logical design and performing wiring between the logical components, and a speed analysis section for performing a speed analysis based on calculation of a delay for each of paths on the design object circuit in accordance with a result of the layout. The logical designing section, the layout designing section and the speed analysis section are connected to each other so as to cooperate with each other when necessary. The interactive circuit designing apparatus is applied to an apparatus for designing a circuit of an LSI, a printed circuit board or a like element.