Does age really matter on workplace if you are well qualified and matured enough?

Age is almost always irrelevant.  In many countries discrimination on the basis of age is illegal.

In professional sport, for example, age is completely irrelevant.  What matters is how fast/strong/quick the person is, not how old they are.

What matters in any job is, do you have the skills and other attributes required?  It may be the case that, in general, people of a one particular age range are more likely to meet the criteria than people in another age range.  However, that does not apply to individual candidates.  A person in the "wrong" age range may in fact be your best candidate.

When I was 25 I was lifting a heavy thing with the help of a man who was about 70.  After a while he told me to get out of his way because I was just being a nuisance.  I was an office worker, whereas he had spent the last 50 years doing heavy manual labour.  He was much, much, stronger than I was.

Generally speaking, it is most certainly not as long as you are physically fit for the job and highly qualified. However, there are some HR practices where they are particular with the age of an applicant because they also base it to the total years of experience and the nature of the job of course. Say for example, here in UAE I normally see job postings where certain job's required age is between 25-35 only. Others prefer 23-28 and not more than that. So age is mostly dependent on company's preferences and country's rules and regulation. 

@Azhar Hasan

It's unfair to divide workforce on the basis of their age. However we can't deny the nature of job and requirement where age sometimes effect overall efficiency of job. There are number of jobs where HR has to consider health and safety measure while selecting the right candidate.

Heavy lifting, tower technician and some highly customer oriented jobs like air hostess and cheer leaders are the name of jobs where selector has to consider the importance of candidate's age.

no، there is always an empty chair for professional people

Experience says Age does matter ! Not all jobs are same. Some required brain and some muscle. No matter how well you are qualified and mature. A person need to choose a different job as he grows older as per his health condition. After all health is a gift to humans from Almighty.