1. A microprogram control device for time-shared control of a plurality of controlled devices each comprising a microinstruction decoder, a microinstruction test circuit, and a microinstruction execution request circuit, said device comprising: a control memory for storing microinstructions for controlling said plurality of controlled devices and for reading out said microinstructions in one machine cycle, a first microinstruction register for storing first type microinstructions read out of said control memory and controlling one controlled device over a plurality of machine cycles, a second microinstruction register for storing second type microinstructions read out of said control memory and controlling one controlled device in one machine cycle, and a microinstruction execution control circuit for receiving input signals consisting of microinstruction-execution-request signals from each of said microinstruction-execution-request circuits of said plurality of controlled devices, first signals from said first microinstructon register and second signals from said second microinstruction register, said microinstruction execution control circuit selecting said second microinstruction register and one controlled device controlled by control signals of said second microinstruction register, which is different from the controlled device then being controlled by said one of said first type microinstructions, when said input signals correspond to a given instruction that one of the first type microinstructions controls one controlled device in a certain machine cycle and then in the next machine cycle, and said microinstruction execution control circuit selecting one of said first and second microinstruction registers and one controlled device controlled by control signals of said selected register of the first and second microinstruction registers, when said input signals correspond to any instruction other than said given instruction, whereby one controlled device controlled by the control signals of said first microinstruction register and the other controlled device controlled by the control signals of said second microinstruction register are effectively controlled in parallel.