A modular robot system comprising N cube-shaped unit robots (100-1 to 1 00-N), wherein N is an integer greater than 2, each cube-shaped unit robot comprising: a cube-shaped housing; a step motor located inside the housing; a controller located inside the housing to control the step motor, wherein the housing has a mounting groove formed on one surface thereof to mount a rotary body (300-1, 300-2) rotating by a rotary shaft of the step motor thereon and connection grooves (141 - 145) with the same shape as each other formed on the five surfaces thereof, so that through connectors mounted on the connection grooves, one cube-shaped unit robot is connectable to another cube-shaped unit robot, wherein the controller is configured to receive any one of different unique identification numbers (ID 1 - ID 4) designated to the N cube-shaped unit robots (100-1 - 100-N) and it is configured to perform a step motor control sequence (1000-1 - 1000-4) corresponding to the unique identification number (ID 1 - ID 4) received among N step motor control sequences (1000-1 - 1000-4), wherein the N step motor control sequences (1000-1 - 1000-4) correspond to N unique identification numbers (ID 1 - ID 4) transmitted to the N cube-shaped unit robots (100-1 - 100-N) previously defined; and a central control terminal for applying the different unique identification numbers (ID 1 - ID 4) to the N cube-shaped unit robots (100-1 - 100-N), wherein the central control terminal is configured to transmit synchronization information to the N cube-shaped unit robots (100-1 - 100-N), the synchronization information comprising synchronization information transmission time point (T 1 - T 3) measured based on a timer operating in the central control terminal, and is configured to transmit control sequence start commands to the N cube-shaped unit robots (100-1 - 100-N), the control sequence start commands comprising start time point (T start) information calculated based on the timer operating in the central control terminal, and wherein the controller is configured to start an own timer thereof if the synchronization information is transmitted to the cube-shaped unit robot and if the control sequence start command is transmitted to the cube-shaped unit robot, is configured to perform the step motor control sequence (1000-1 - 1000-4) at the start time point (T start) using the synchronization information transmission time point (T 1 - T 3) of the synchronization information and the own timer thereof. a cube-shaped housing; a step motor located inside the housing; a controller located inside the housing to control the step motor, wherein the housing has a mounting groove formed on one surface thereof to mount a rotary body (300-1, 300-2) rotating by a rotary shaft of the step motor thereon and connection grooves (141 - 145) with the same shape as each other formed on the five surfaces thereof, so that through connectors mounted on the connection grooves, one cube-shaped unit robot is connectable to another cube-shaped unit robot, wherein the controller is configured to receive any one of different unique identification numbers (ID 1 - ID 4) designated to the N cube-shaped unit robots (100-1 - 100-N) and it is configured to perform a step motor control sequence (1000-1 - 1000-4) corresponding to the unique identification number (ID 1 - ID 4) received among N step motor control sequences (1000-1 - 1000-4), wherein the N step motor control sequences (1000-1 - 1000-4) correspond to N unique identification numbers (ID 1 - ID 4) transmitted to the N cube-shaped unit robots (100-1 - 100-N) previously defined; and a central control terminal for applying the different unique identification numbers (ID 1 - ID 4) to the N cube-shaped unit robots (100-1 - 100-N), wherein the central control terminal is configured to transmit synchronization information to the N cube-shaped unit robots (100-1 - 100-N), the synchronization information comprising synchronization information transmission time point (T 1 - T 3) measured based on a timer operating in the central control terminal, and is configured to transmit control sequence start commands to the N cube-shaped unit robots (100-1 - 100-N), the control sequence start commands comprising start time point (T start) information calculated based on the timer operating in the central control terminal, and wherein the controller is configured to start an own timer thereof if the synchronization information is transmitted to the cube-shaped unit robot and if the control sequence start command is transmitted to the cube-shaped unit robot, is configured to perform the step motor control sequence (1000-1 - 1000-4) at the start time point (T start) using the synchronization information transmission time point (T 1 - T 3) of the synchronization information and the own timer thereof.