SQL & PL/SQL

while exceuting this procedure m getting error even when i handled with exception.

set serveroutput on
create or replace procedure ad(id number,name varchar,did number)
is
fk_constraint exception;

begin
insert into es values(id,'name',did);
if SQL%NOTFOUND then
raise fk_constraint;
end if;
rollback;
exception
when fk_constraint then
dbms_output.put_line('INVALID DEPT');
end;

/
execute ad(1500,'avc',11);

can anyone help me to resolve this.