Amorphous Boron Nitride (a-BN) is an important starting material for the synthesis of cubic BN(o-BN). However, information on the synthesis methods and the characteristics of a-BN are not sufficiently discussed in the literature. The purpose of this study is to understand the conversion of precursor chemicals to a-BN and to illustrate the effects of starting material and heat treatment conditions on the formation and characteristics of a-BN. Boric acid (H3BO3) and melamine (C3H6N5) were used as starting materials and the starting composition range was selected to be between 1:1 and 6:1 molar ratios (HBOi^HsNe). Two-step solid state reaction method was applied for the synthesis of a-BN: First heat-treatment at 200°C for 2 hours in air and the second heat treatment at selected temperatures for 3 hours in N2 gas atmosphere. To determine the condition region for the synthesis of a-BN, synthesized powders were characterized using X-ray diffraction, Raman and FTIR spectroscopies which showed different sensitivity for detecting crystalline phase in the powders. The condition regions for the synthesis of a-BN were determined to be between 400°C and 600°C for the composition range of 1:1 and 1.5:1. Crystallization was observed at lower temperatures for the samples with higher H3BO3 content in the H3BO3-C3H6N5 system.