coil can be increased it is therefore advantageous in that the torque required to perform carriage drive is outputted and the head drive actuator itself can be made thinner moreover because the step motor of this embodiment applies a general bipolar method as its drive method a drive circuit on the market can be employed this embodiment shows one example of the recording medium cartridge of this invention 0267 fig3 a and fig3 b show the state in which a shutter is being closed 0268 fig3 a gives its top view and fig3 b is the side view fig3 a and fig3 b show the opening state of the shutter fig3 a is the top view and fig3 b is the side view in the figures an opener band 306 an opener latch 307 guide rollers 308 and 309 are shown although not shown in the figures this construction is possible to apply tension to at least one point of opener band 306 opener band 306 is connected with shutter 304 on its both ends and connected with opener latch 307 in halfway as shown in fig3 a when recording medium cartridge 300 is inserted into the direction of x opener latch 307 is moved toward the direction of x by the lever provided to the storage device as this opener latch 307 and shutter 304 connected with each other by opener band 306 are pulled in the y direction window 305 is released thereupon exposing recording medium 301 at this time no part material for cartridge case 302 nor part material for shutter 304 exist in area s in order to pull out recording medium cartridge 300 in the opposite direction opener latch 307 is moved in the x direction by the lever of the.