i don't want change the width of the bar, i want change the distance between each bar.
Then you just need to edit width of your worksheet. If you have scrollbar down there, just change it to use entire view and then make that sheet narrower.
can tell me how to change the size of the worksheet, i really don't know how to change it.
Put your worksheet into dashboard and then you can change the size in many ways for example by adding blank sheet next to your bar graph and then resize:
Add worksheet into dashboard and blank next to it
Resize worksheet by moving right border
And then go back to your original worksheet and resize your bars to original size