How to find the max salary of employee of each department ?

read :
SQL GROUP BY Statement[^]
SQL MAX() Function[^]
SQL INNER JOIN [^]

sample sql query (I assume you have salary in emp table)

SELECT MAX(E.SALARY), D.DEPNAME FROM EMP E
JOIN DEPT D ON E.EMPID = D.EMPID
GROUP BY D.DEPNAME

What have you tried so far?

And looking at the Table structure, I don't even find the salary column itself. So, how do you know what the Salary is.

The current table structure is not even normalised.
Anyway, if I were you I would first restructure the tables as:

Employee:
	Id,
	Name,
	Age,
	Salary,
	DepartmentId

Department:
	Id,
	Name

Apart from that I would suggest you to look at following topics (atleast) in SQL:

MAX

http://www.w3schools.com/sql/sql_join.asp[^]

GroupBy

http://www.w3schools.com/sql/sql_groupby.asp[^]

Joins

http://www.w3schools.com/sql/sql_join.asp[^]

I suggest you try it out writing yourself and show us what have you tried. And if you still have questions, someone here would help you.