Can Someone teach me how to design joomla template….is there any software that we can create joomla template??
Firstly let me reassure you that it is not that complicated to learn. The very essence of a CMS like Joomla is to make things easy for you – and that includes template design. You don’t need to spend any money nor have fancy software.
Start with a basic one from a tutorial (see below) and edit it. You can use Notepad (Win) or Textedit (Mac) but I would recommend free editors like Notepad+ (Win) or TextWrangler (Mac) which allow things like multiple file editing and code highlighting.
Which version are you going to install?
1.5 is the latest but work is still in progress on official template documentation and tutorials.
Luckily however two of my favorite sites have great tutorials and starter templates:
Compass Designs:
http://www.compassdesigns.net/tutorials/joomla-tutorials/joomla-1.5-template-tutorial.html
and Rocket Themes:
http://tutorials.rockettheme.com
If you prefer not to "move with the times" 1.0.14 is the older (more stable) version of Joomla and there are good official templates in the help section of the joomla.org site.
There are websites which offer tempaltes typically functioning as non-exclusive template clubs. They can give you enough flexibility to personalise your site and a wide range to choose from and you can change when you want, for example:
http://www.yootheme.com
or
http://www.rockettheme.com
Remember that a template is ALWAYS downloadable and editable by you 
.