There are specific standard refusal reasons which fit this situation:
You have not provided proof of sufficient means of subsistence, for the duration of the intended stay or for the return to the country of origin or residence, or for the transit to a third country into which you are certain to be admitted, or you are not in a position to acquire such means lawfully.
The information submitted regarding justification for the purpose and conditions of the intended stay was not reliable.
The first reason means that you must show you have enough money to afford all of the expenses of your trip: plane tickets, hotel, food, etc. and that you must have obtained this money through legal means.
The second reason is more complex. It means in general that the overall application must make sense and the documents submitted must be genuine and related to the declared purpose of the visit. (We have a lengthy explanation of what to do about this refusal reason.)
If you have to take a loan to afford the trip, then the consular officer will be inclined to believe that you cannot truly afford the visit on your own. He or she may think that you instead plan to come to Europe to live and work illegally. Whether you actually intend that or not, the officer will still refuse the visa.
It is best to pay for such a visit from your own personal savings, and to have personal circumstances which permit you to save enough money on your own to afford such a visit. It is possible for a family member or very close friend to sponsor you and provide the money for your trip, but the reason for that person to pay for your expenses must be carefully justified in the visa application.