The present book "Quantum mechanics, Atomic and Molecular Physics" is written for B.Sc. III year of all Indian universities, especially for the universities of Rajasthan state. The present book will also useful for the students of post graduate classes of physics and for the competitive examines. In the present book not only a large number of solved problems asked in the different types of examination of various universities have been given but also the self explanatory diagram have been included to understand the applications of various principles discussed in the chapter. The book is divided into 11 chapter; first seven chapter are related to background of quantum mechanics in which photo electric effect, Compton effect, Schrodinger's equation and their applications are explanied in a systematic manner. The operators and its applications are explained in a systematic manner. The operators and its applications are also given in these chapter. In the application part of Schrodinger's equation the infinite and finite potential well, step potential barrier and rectangular barrier is describe in detail. The last four chapter of the book are related to atomic and molecular physics and their spectroscopy, in which the spectrum based on selection rules, are explained. In these chapter Raman spectroscopy is also given with their principle diagram. To avoid the problem of keeping syllabus, a copy of it has been included in the present book in the beginning. As an exercise to the students, multiple type of questions, short answer type question and descriptive type of questions are also included at the end of each chapter. Contents of the book are also included at the beginnings so that the students and teachers can easily find the topic related to them. It is hoped the above features of the book make it unique from others. We express our deepest sense of gratitude to all the professors and teachers, who helped us in writing this book in very small time duration. Several books and journals on the subjects have been refereed in preparation of the book in present mode. Gratitude is also expressed to them.