The law of supply is a fundamental principle of economic theory which states that, keeping other factors constant, an increase in price results in an increase in quantity supplied. In other words, there is a direct relationship between price and quantity: quantities respond in the same direction as price changes. This means that producers are willing to offer more of a product for sale on the market at higher prices by increasing production as a way of increasing profits. In short, the law of supply is a positive relationship between quantity supplied and price and is the reason for the upward slope of the supply curve. Some heterodox economists, such as Steve Keen and Dirk Ehnts, dispute the law of supply, arguing that the supply curve for mass produced goods is often downward-sloping: as production increases, unit prices go down, and conversely, if demand is very low, unit prices go up. This corresponds to economies of scale. Definition To know law of supply, we should know what is supply previously. Supply is the quantity of a good or service that producers are willing and able to provide at a given price, at a given time. [5] Law of supply is the microeconomic law explaining the characteristic of the supply, stating that “ All other factors being equal, as the price of a good or service increases, the quantity of goods or services that suppliers offer will increase, and vice versa. The law of supply says that as the price of an item goes up, suppliers will attempt to maximize their profits by increasing the number of items for sale.” [6], [7] This is because as the price goes higher producers will be more willing to provide more of their goods or services; every business exists to make profit and price increasing gives signal to producer to increase their price to make more profit therefore higher price is inducing producers to make more. [6] We can easily find adequate metaphor even in the university to understand the concept of Law of Supply. If the wage paying to computer engineer increases, there will be more students will choose to study computer science. As well as in business, if the profitability of the product increases, the firm will decide to manufacture more goods. [6] Formula This characteristic of supply can be expressed in mathematical formula in linear equation, shape of rightwards and upwards.